Pediatric Annals

Computed Tomographic Imaging of Abdominal Abnormalities in Infancy and Childhood

Jerald P Kuhn, MD; Paul E Berger, MD

Abstract

1. Webster, E. W., Alpert, N. M., and Brown ell, G. L. Radiation doses in pediatrie nuclear medicine and diagnostic x-ray procedures. In James, A. E., Wagner, H. M., and Cook, R. E. (eds.): Pediatrie Nuclear Medicine. Philadelphia: W. B. Saunders Company, 1974, pp. 34-58.

2. Seppanen, U., Tomiainen, P., and KiviniitEy, K. Radiation gonad doses received by children in intravenous urography and micturition cystourethrography. Pediatr Radial 8 (1979), 169-172.

3. McCullough, E. C., and Paint, J. Patient dose in computed tomography radiation. Radiology 129 (1978), 457-463.

4. Brasch, R. G., Boyd, D. F., and G coding, C. A. Computed tomographic scanning in children; comparison of radiation dose and resolving power of commercial CT scanners. Am. ]. Roentgenol. 131 (1978), 95-101.

5. Berger, P. E.. Munschauer, R. W., and Kühn, J. P, Computed tomography and ultrasound of renal and peri renai diseases in infants and children: relationship to excretory urography in renal cystic disease, trauma and neoplasm. Pediatr. Radial (In press.)

6. Muhm, J. R., Brown, L. R., and Crowe. J. K. Use of computed tomography in the detection of pulmonary nodules. Mayo Clinic Proc. 52 (1977), 345-348.

7. Hailer, J. O., et al. Left adrenal neuorblastoma with n orma I -appearing urogram. Am- ]. Roentgenol. 129 (1977), 1051-1055.

8. Berger, P. E., Kühn, J. P., and Munschauer, R. W. Computed tomography and ultrasound in the diagnosis and management of neuroblastoma. Radiology 128 (1978), 663-667.

9. Lee, I. K. T., Stanley, R. J., Sagel, 5. S.. and Levitt, R. G. Accuracy of computed tomography in detecting intraabdominal and pelvic adenopathy in lymphoma. Am. }. RoentgenoJ. 131 (1978), 311-315.

10. Callen P. W., Filly, R. A., and Korobkin, M. Computed tomographic evaluation of the diaphragmatic crura. Radiology 126 (1978), 413-416.

11. Berger, P. E., and Kühn, J. P. Computed tomography of tumors of the musculoskeletal system in children: clinkal applications. Radiology 127 (1978), 171-175.

12. Korobkin, M., et al. Comparison of computed tomography, ultrasound, and gallium 67 scanning in evaluation of suspected abdominal abscess. Radiology 129 (1978), 89.

13. Kühn, J. P., Berger, P. E., and Munschauer, R. W. Computed tomographic diagnosis of hidden abdominal abscess in children. Ann. Radial. 23(1980), 153-158.

14. Royal, S. A., Goldberg, H. 1., and Thaler, M. M. Evaluation of childhood cryptogenic hepatomegaly by computed tomography. Paper presented at the 22nd annual meeting, Society for Pediatrie Radiology, March, 1979.

TABLE 1

RADIATION EXPOSURES IN VARIOUS IMAGING PROCEDURES

TABLE 2

COMPARATIVE COSTS OF VARIOUS IMAGING MODALITIES - 1980

TABLE 3

DILUTION OF CONTRAST MATERIAL FOR OPACIFICATION OF SMALL BOWEL AND STOMACH IN PEDIATRIC PATIENTS

TABLE 4

RENALTRAUMA: COMPARISON OF FINDINGS BY INTRAVENOUS PYELOGRAM, ULTRASOUND, AND COMPUTED TOMOGRAPHY IN SEVEN CHILDREN…

Computed tomography (CT) is the most powerful imaging tool available to the diagnostic radiologist. It has proved to be of clinical value in examining children with a variety of abdominal abnormalities. It makes it possible to more clearly define the normal and pathologic anatomy in the infant and the child through the use of a three-dimensional perspective, providing definite diagnoses that would not be possible through the use of more conventional techniques.

ADVANTAGES OF COMPUTED TOMOGRAPHY

Computed tomography provides imaging superior to that possible with other techniques in three ways: the axial tomographic view is free of confusing shadows or shapes caused by structures lying between the imaging instrument and the target organ, there is increased contrast resolution, and the technique makes it possible to measure tissue densities.

Freedom from confusing superimposed shadows seen on x-ray imaging is possible in the axial tomographic view, in which a thin anatomic crosssectional image is obtained. Such organ margins as the anterior and posterior renal borders, which are not seen on conventional radiographie examinations, are clearly visible on computed tomographs.

Table

TABLE 1RADIATION EXPOSURES IN VARIOUS IMAGING PROCEDURES

TABLE 1

RADIATION EXPOSURES IN VARIOUS IMAGING PROCEDURES

Increased contrast resolution results from superior density discrimination (plus or minus 0.05 percent), making visible such soft-tissue structures as the adrenals, the pancreas, and hepatic parenchymal details, which are invisible on conventional radiographie examinations.

Tissue densities can be measured, since linear absorption coefficients of the x-ray beam can be measured and assigned arbitrary numbers. A range of values can then be determined for normal organs, and some information can be learned regarding the make-up of both normal and abnormal structures. For instance, differentiation can be made between a cystic mass, which is of water density, and a lesion arising from tissues of fatty origin; these, in turn, can be distinguished from masses composed of solid neoplastic tissue.

DISADVANTAGES OF CT

Despite these significant advantages, CT is not the ideal imaging technique for pediatrie radiology because of a number of limitations. These include the fact that radiation is used and that the procedure is expensive. There are limitations inherent in the technique, and these are compounded by the small size of the structures in many children. There are also problems caused when young patients move and by the fact that there are no scanners in many communities.

Ionizing radiation is a consequence of CT, as indeed it is of all imaging techniques, with the exception of ultrasound. The amount of radiation the child will receive will vary with the number of "cuts," or sections, made, the kind of machine, and the technical factors used. As can be seen in Table 1 , the radiation required for CT is not much more than needed for other imaging techniques and considerably less than for some. Furthermore, exposure to radiation during CT is limited sharply to the area examined; there is very little scattered radiation to such critical organs as the thyroid, the lens, or the gonads - unless, of course, they are the organs being examined. For example, a CT scan of the abdomen will require more radiation to the skin but less to the gonads than a barium enema.

The cost-benefit ratio between radiation exposure necessary and the diagnostic information must be considered when comparing CT with other diagnostic examinations. In general, CT gives more diagnostic information than other techniques - usually more than all the conventional radiographie techniques combined. Furthermore, it should be remembered that usually when a child is having a CT examination, serious illness - often a possible malignancy - is suspected.

Limitations that are inherent in the technique itself include the fact that the examination is generally limited to the axial view only, making evaluation of longitudinal structures, such as the vena cava or the ureters, somewhat difficult. Thin structures, such as the diaphragms, which are parallel to the axial plane, are not as well imaged as they would be in the longitudinal plane. Artifacts that appear on the sonograph to be authentic may be produced by high-density structures, such as clips - especially if there is motion.

Limitations are also imposed by the child himself. Most important of these are the small size of the structures being examined in infants and small children and the fact that many of these structures are not surrounded by body fat, as they are in older persons, making delineation of the anatomy less clear than in the adult patient. For instance, normal-sized lymph nodes are usually easily seen in the adult retroperitoneum but are nearly impossible to see in children. Lack of body fat means that contrast material must be used much more frequently in the child to opacify the vessels and the intestinal tract so as to better separate these normal structures from pathologic ones.

There are also socioeconomic limitations to CT. The technique still is not available for evaluating most children in the United States, for most scanners are in large medical centers, and here the primary orientation is usually toward diagnosing and treating the adult. CT examination is expensive, and its cost must be determined in comparison with information that could be gained from other techniques that are available and cost less,* The costs for a day of hospitalization plus the cost of various types of diagnostic examinations in Buffalo, N. Y. , are shown in Table 2. The table indicates that, while CT is indeed expensive, it is not much more expensive than a combination of any two of the other diagnostic tests.

It has been our experience that several tests are frequently done, particularly when it is necessary to assess the cause of an abdominal mass. We believe that the most cost-effective method in a child with a suspected malignant tumor is to go relatively soon to CT in the course of the diagnostic workup, omitting many of the standard tests, which in most instances give less information than the CT examination.

TECHNIQUE

For optimal examination in a child, it is necessary to use a scanner with a short scan time: our current unit makes one section in two seconds. Motion by the patient or even physiologic motion of his organs - e.g. , the beating of the heart or peristaltic contraction of the intestine - can cause significant degradation of the CT image. In general, no particular patient preparation is needed, although barium in the intestinal tract interferes with the CT image, so one should be careful to avoid a barium contrast study before doing a CT study. Patients under the age of two often have to be sedated, but general anesthesia is rarely ever necessary.

The examination must be tailored to the clinical situation according to the information sought and the age of the patient. If the suspected clinical problem is one in which normal bowel could conceivably be confused with tumor or abscess, then it is necessary to opacify the small bowel with dilute contrast material. We use diatrizoate (Castrografin) in the dilution shown in Table 3. In this strength, there is no hazard of hypertonic dehydration. If the pelvis is the area of interest, it may be necessary to use a low Gastrografin enema to outline the rectosigmoid colon. Thirty minutes after the opaque medium is drunk, the small bowel is usually fairly well opacified and the area of interest can be scanned. A slice thickness of 1 cm. is used, and contiguous sections are obtained through the area of interest. Frequently it is necessary to reexamine the area of interest with intravenous contrast material injected as a bolus (3cc./kg.)while performing the scan. This technique delineates the arteries and veins of the region as well as opacifying the organs, allowing better anatomic definition of both normal and pathologic anatomy.

Table

TABLE 2COMPARATIVE COSTS OF VARIOUS IMAGING MODALITIES - 1980

TABLE 2

COMPARATIVE COSTS OF VARIOUS IMAGING MODALITIES - 1980

Table

TABLE 3DILUTION OF CONTRAST MATERIAL FOR OPACIFICATION OF SMALL BOWEL AND STOMACH IN PEDIATRIC PATIENTS

TABLE 3

DILUTION OF CONTRAST MATERIAL FOR OPACIFICATION OF SMALL BOWEL AND STOMACH IN PEDIATRIC PATIENTS

INDICATIONS FOR CT

There are four indications for CT in diagnosing abdominal abnormalities in infancy and childhood: presence oían abdominal mass, abdominal abscesses under certain conditions, abdominal trauma, and parenchymal liver disease.

Diagnosis of an abdominal mass in a child still begins with the traditional methods - obtaining a history, making a physical examination, and ordering plain-film radiographie studies. If the mass shown by these methods does not appear to be related to the gastrointestinal tract, we would next do an ultrasound study.* Most pédiatrie abdominal masses are benign and cystic and arise from the genitourinary tract. While CT can delineate these beautifully, it generally is not necessary if the diagnosis can be established quite well by ultrasound.

The ultrasound examination may give equivocal findings, however, and in such cases CT should be useful. In children with tuberous sclerosis, for example, excretory urography may show evidence of polycystic disease, angiomyolipomas, or both. Although the differentiation can be made by ultrasound, it is made more readily with CT.

In patients in whom the ultrasound study has shown a solid lesion, our practice is to proceed directly to CT, since the intravenous pyelogram rarely, if ever, gives information that is not obtained on a CT, while the CT provides far more information than the urogram.5

There are two main reasons for doing CT in the detection of solid-mass lesions. The first is to increase diagnostic accuracy. Conventional methods, especially with the addition of ultrasound, are already excellent; CT does, however, provide a small but definite increment in the accuracy of the diagnosis in these potentially fatal diseases. A second and perhaps more important reason for doing CT is to accurately determine the extent of disease. The extent of disease at the time of diagnosis is the most important factor in the prognosis for that affected patient.5 Computed tomography provides this information far more accurately than any combination of other available diagnostic radiologie tests. The importance of CT varies somewhat with the condition suspected, but, of course, often the diagnosis is not known when the patient is first examined. Following are some examples of where CT has been helpful in assessing abdominal masses.

Wilms' tumor. Computed tomography is indicated in children with suspected Wilms' tumor even though it may be less important than it is in assessing some other abdominal malignancies of childhood. We have studied 10 children with known or suspected Wilm's tumor. In two cases the initial diagnosis was changed by CT and in another large locally recurrent tumor was detected. In most of the other cases, specific important information about the extent of tumor was obtained. For instance, the surgeon needs to know whether the inferior vena cava is invaded by tumor, and with a bolus-injection technique we can routinely visualize the vava to exclude gross intracaval tumor (Figure 1). Frequently the renal veins are seen (Figure 2), and in one patient we were able to diagnose extension of tumor into the left renal vein even though the tumor had not yet extended into the inferior vena cava. Detection of a second primary tumor in the opposite kidney is another important goal of the initial study. We have not yet seen such a case, but since the normal structures are so clearly seen (Figure 3), it seems likely that this pathology when present should be detected.

Figure 1. An intravenous urogram of a live-year-old boy showed typical findings of a Wilms' tumor. Computed tomographic scan above made after injection of contrast material shows the aorta (A) and inferior vena cava (IVC) to be patent and not displaced. The large Wilms' tumor (VvT) is clearly shown arising from the central portion of the left kidney (LK). The right kidney (RK) appears entirely normal.

Figure 1. An intravenous urogram of a live-year-old boy showed typical findings of a Wilms' tumor. Computed tomographic scan above made after injection of contrast material shows the aorta (A) and inferior vena cava (IVC) to be patent and not displaced. The large Wilms' tumor (VvT) is clearly shown arising from the central portion of the left kidney (LK). The right kidney (RK) appears entirely normal.

An additional reason for doing CT is that the surgeons believe that the actual operation itself is made easier by the graphic CT image's allowing them to see the extent of the tumor and its relationship to surrounding organs.

Computed tomography is also useful in the detection and follow-up of lung métastases in Wilms' tumor and is being used routinely in our practice instead of conventional whole-lung tomography. Computed tomography has been shown in adults to detect many more long nodules than either conventional tomography or plain films.6 The problem has been that all nodules so identified are not malignant: many are granulomatous. Our experience has been that in children granulomas are far less common and the nodule found in the lungs of a child with known malignancy has a very high likelihood of being a metastasis.

Figure 2. A four-year-old girl with a Wilms' tumor diagnosed on a urogram made at another hospital. Patient admitted for surgery. This single magnified CT image made after contrast injection outlines the inferior vena cana (ive) and left renal vein displaced anteriorty (outlined by three small black arrows), and the renal artery (outlined by three white arrowheads) is shown to be elevated by tumor mass large black arrow) situated between the kidney and renal artery. Findings were confirmed at surgery.

Figure 2. A four-year-old girl with a Wilms' tumor diagnosed on a urogram made at another hospital. Patient admitted for surgery. This single magnified CT image made after contrast injection outlines the inferior vena cana (ive) and left renal vein displaced anteriorty (outlined by three small black arrows), and the renal artery (outlined by three white arrowheads) is shown to be elevated by tumor mass large black arrow) situated between the kidney and renal artery. Findings were confirmed at surgery.

Figure 3. Magnified image of a normal CT scan made during the early injection phase. The spine (SP) is seen at left. Cortical medullary differentiation is clearly seen at this early phase. Renal pyramids can be recognized and the width of the cortex accurately measured.

Figure 3. Magnified image of a normal CT scan made during the early injection phase. The spine (SP) is seen at left. Cortical medullary differentiation is clearly seen at this early phase. Renal pyramids can be recognized and the width of the cortex accurately measured.

Neuroblastoma. We have performed more than 50 abdominal examinations in children with known or suspected neuroblastoma and feel that CT is by far superior to any other modality or combination of modalities in both initial and follow-up diagnosis of these children. Usually the initial diagnosis is straightforward with conventional techniques, although normal intravenous urograms have been reported in the left adrenal neuroblastoma.7 Computed tomography can clarify the diagnosis in these few doubtful cases and will nearly always give other information about the extent of the tumor, including its relationship to the great vessels (Figure 4), possible paraspinal extension, or liver involvement. Additionally, because of its clear anatomic portrayal, CT is the method of choice for follow-up radiologie evaluation.8 We have seen several cases in which the follow-up intravenous pyelogram was normal and CT detected significant residual or recurrent disease (Figure 5), and we no longer use excretory urography in routine follow-up because CT has far greater sensitivity and specificity. At first, ultrasound examinations were also used in all these children, but we now reserve ultrasound for selected cases to analyze indeterminate findings on the CT scan - e.g., if the inferior vena cava is not well seen or if the region around the head of the pancreas is not clearly distinct from surrounding vascular or nodal structures.

Figure 4. A one-year-old with left adrenal neuroblastoma. The CT scan clearly shows the size and extent of the tumor, which is enormously larger than was suspected from the urogram. Lateral tumor margins are outlined by the large white arrows. Note the displacement anteriorly and laterally of the inferior vena cava (ive). The tumor surrounds the aorta (a) and superior mesenteric artery (two small white arrows).

Figure 4. A one-year-old with left adrenal neuroblastoma. The CT scan clearly shows the size and extent of the tumor, which is enormously larger than was suspected from the urogram. Lateral tumor margins are outlined by the large white arrows. Note the displacement anteriorly and laterally of the inferior vena cava (ive). The tumor surrounds the aorta (a) and superior mesenteric artery (two small white arrows).

Figure 5. In a three-year-old with previous neuroblastoma, recurrence was suspected because of elevation of vanillylmandelic acid, but routine intravenous urogram was normal. The CT scan above the level of the kidneys shows a huge prevertebral mass extending anteriorly, outlined by the white arrows. The liver (L) is normal.

Figure 5. In a three-year-old with previous neuroblastoma, recurrence was suspected because of elevation of vanillylmandelic acid, but routine intravenous urogram was normal. The CT scan above the level of the kidneys shows a huge prevertebral mass extending anteriorly, outlined by the white arrows. The liver (L) is normal.

Primary hepatic tumors. Primary hepatic tumors are relatively uncommon in pediatrics, but CT has provided important information about the character and extent of mass lesions in the liver in a few such children (Figure 6). The normal hepatic anatomy is well portrayed on CT, and frequently the division of the liver into the right and left lobes is recognizable. However, before undertaking resection the surgeon may still desire angiography to aid the operative approach.

Figure 6. A one-year-old child with an abdominal mass. The CT scan shows a multichambered, mostly cystic, mass occupying essentially the entire right lobe of the liver. Note the normal left lobe (LL). At surgery this proved to be a cystic mesenchymal hamartoma of the right tobe of the liver.

Figure 6. A one-year-old child with an abdominal mass. The CT scan shows a multichambered, mostly cystic, mass occupying essentially the entire right lobe of the liver. Note the normal left lobe (LL). At surgery this proved to be a cystic mesenchymal hamartoma of the right tobe of the liver.

Lymphoma. We have studied more than 30 patients with abdominal lymphoma, While normalsized lymph nodes can be commonly seen in adults,9 they are only rarely visible in children. Furthermore, CT cannot differentiate between normal nodes and normal-sized nodes that are replaced with tumor but not enlarged. However, bulky disease has been clearly evident in our experience (Figure 7). Therefore our current practice is to use CT for initial examination - if bulky disease is seen below the diaphragms, a lymphangiogram or staging laparotomy is usually not necessary. If the CT examination is negative and accurate staging is still required, either a lymphangiogram or staging laparotomy will be necessary. This approach requires careful technique to avoid false-positive CT examinations. Nonopacified bowel can simulate enlarged nodes, so every effort must be made to fill questionable areas with contrast material. Occasionally a prominent diaphragmatic crus can simulate nodal enlargement as well.10

Figure 7. Prevertebral lymph node mass' is seen (white arrows) surrounding the inferior vena cava (i) and the aorta (a), which have been opacified by intravenous contrast material. Note also the metastatic lesion in the liver.

Figure 7. Prevertebral lymph node mass' is seen (white arrows) surrounding the inferior vena cava (i) and the aorta (a), which have been opacified by intravenous contrast material. Note also the metastatic lesion in the liver.

Ultrasound has been helpful in some cases of abdominal lymphoma but confusing in others and frequently has been nondiagnostic because of obscuration of the prevertebral para-aortic region by overlying gas.

Other retroperitoneal tumors. Other miscellaneous retroperitoneal tumors are teratoma, rhabdosarcoma, other sarcomas, and other uncommon adrenal lesions. Computed tomography has been very helpful in diagnosis and management of this mixed group of conditions because it provides such clear depiction of this previously invisible area (Figure 8).

Pelvic masses. In the diagnosis of pelvic masses, ultrasound is used first unless the mass is known to be malignant. For cystic or congenital masses or for those thought to be due to pregnancy or a gynecologic abnormality, or for inflammatory masses, usually the assay can cease with the ultrasound examination. If a malignant mass is present, CT provides excellent information about the extent of the disease, particularly the relationship to the bones and muscle planes (Figure 9).11

Figure 8. A one-year-old child with a calcified right suprarenal lesion thought to represent neuroblastoma. Instead, a large teratoma was diagnosed on CT scan. Note the dark, fatty elements outlined by the black heavy arrows, the bone outlined by the open arrowhead, and the cystic component identified (C).

Figure 8. A one-year-old child with a calcified right suprarenal lesion thought to represent neuroblastoma. Instead, a large teratoma was diagnosed on CT scan. Note the dark, fatty elements outlined by the black heavy arrows, the bone outlined by the open arrowhead, and the cystic component identified (C).

Figure 9. A teenage girl with a pelvic Ewing's sarcoma thought clinically to be doing well without evidence of recurrence. Computed tomogram shows a large intrapelvic mass extending medially from the lateral pelvic wall, outlined by white arrows. Note the mud effacement of the bladder and rectum but the clear separation of the mass from these structures.

Figure 9. A teenage girl with a pelvic Ewing's sarcoma thought clinically to be doing well without evidence of recurrence. Computed tomogram shows a large intrapelvic mass extending medially from the lateral pelvic wall, outlined by white arrows. Note the mud effacement of the bladder and rectum but the clear separation of the mass from these structures.

Paraspinal masses. Paraspinal and intraspinal anatomy is much more clearly seen with CT than with other techniques. Frequently, intraspinaí extension of tumor can be identified on the conventional CT examination. If there is a question either from this examination or from the clinical picture, CT using metrizamide injected into the spinal subarachnoid space provides exquisite delineation of the normal spinal-cord anatomy and can clearly depict intraspinal extension of tumor or congenital mass.

Diagnosis of abdominal abscesses can be made by ultrasound, CT, or gallium scanning,12 but in our experience13 CT is the most accurate. In a study of 25 children, we found that gallium scanning provided a significant number of false-positive reports when the "abscess" was actually due to inflammatory bowel disease or lymphoma or - on two occasions - persistent gallium accumulation in a normal bowel. Ultrasound also provided falsepositive reports because of the nonspecific nature of the mass identified compounded by the less complete anatomic visualization seen on ultrasound. Two false negatives occurred with ultrasound, once when the location of the abscess was not suspected clinically and therefore not examined on ultrasound and once because the area in question was obscured by overlying gas. Our present diagnostic work-up of a child with an abscess is largely dictated by the clinical situation. If a pelvic collection is suspected, especially in a female, ultrasound is the first diagnostic choice because of the lack of radiation and the fact that this area is as well seen on ultrasound as on CT.

The right subphrenic area is at least as well studied by ultrasound as by CT, and ultrasound would also be used here initially. The left subphrenic area, however, is better examined on CT.

If the clinical situation is not urgent or if the patient has a fever of unknown origin without localizing signs, a gallium scan may be done first and often may be sufficient to detect or exclude an abscess. Computed tomography is most useful in the following situations: (1) when other studies are equivocal, (2) when the extent of disease needs to be accurately identified for surgical purposes, (3) when the patient is acutely ill, (4) in the post-operative patient, (5) in the patient with known inflammatory bowel disease, and (6) when the patient presents with a mass and fever and the initial diagnosis is unclear.

Serious blunt abdominal trauma is an occurrence in which CT can be most useful. In examining seven children with suspected serious renal injury, we found that CT had an advantage over ultrasound in that it demonstrated both anatomy and function while more clearly delineating renal and perirenal pathology, especially renal laceration and intrarenal hematoma. We have found that CT is superior to the intravenous pyelogram in these patients by much more accurately determining extent of renal injury, usually significantly underestimated on excretory urography (Figure 10, Table 4).s Because it is not organ-specific, CT has serendipitously identified hepatic injury in one case and splenic injury in two cases when the clinical concern was over possible renal injury. It might be argued that since these patients are usually treated conservatively, the excretory urogram will suffice. However, we feel that if any examination need be done it is CT that best defines the extent of injury and provides an easy modality for accurate follow-up. In addition, accurately knowing the extent of injury may result in more appropriate conservative management, resulting in a snorter hospital stay and an earlier return to activity.

Figure 10. Computed-tomography scan through the upper renal area of a boy who had suffered trauma to the left kidney. The scan dramatically outlines the perirenal hematoma (white arrows). Note that the anterior portion of the upper renal pole appears extensively macerated compared with the opposite, normal kidney. An IVP made previously showed mild straightening of the left ureter and a suspicion of a perirenal hematoma.

Figure 10. Computed-tomography scan through the upper renal area of a boy who had suffered trauma to the left kidney. The scan dramatically outlines the perirenal hematoma (white arrows). Note that the anterior portion of the upper renal pole appears extensively macerated compared with the opposite, normal kidney. An IVP made previously showed mild straightening of the left ureter and a suspicion of a perirenal hematoma.

Table

TABLE 4RENALTRAUMA: COMPARISON OF FINDINGS BY INTRAVENOUS PYELOGRAM, ULTRASOUND, AND COMPUTED TOMOGRAPHY IN SEVEN CHILDREN

TABLE 4

RENALTRAUMA: COMPARISON OF FINDINGS BY INTRAVENOUS PYELOGRAM, ULTRASOUND, AND COMPUTED TOMOGRAPHY IN SEVEN CHILDREN

Injury to the liver, spleen, and pancreas can all be detected by CT, as can the presence of intraperitoneal blood. Intravenous contrast material Js usually necessary for optimal delineation of intrahepatic hematoma (Figure 11). While we are confident about the use of CT in diagnosing liver hematomas, the accuracy of CT in splenic injury compared with that of radionuclide scanning is still not clear. Occasionally, because of rib artifacts related to motion, the spleen can be difficult to examine.

Figure 11. A 17-year-old boy with Christmas-factor disease was hit in the abdomen by his brother. Note the presence of free intraperitoneal blood in Morrison's pouch (double white arrows), fracture of the posterior portion of the spleen (white arrowheads), and normal-appearing splenic vein and superior mesenterio vein (black arrows). The kidneys bilaterally are normal. The findings were confirmed at surgery.

Figure 11. A 17-year-old boy with Christmas-factor disease was hit in the abdomen by his brother. Note the presence of free intraperitoneal blood in Morrison's pouch (double white arrows), fracture of the posterior portion of the spleen (white arrowheads), and normal-appearing splenic vein and superior mesenterio vein (black arrows). The kidneys bilaterally are normal. The findings were confirmed at surgery.

Diagnosis of certain childhood liver disorders can be made by CT, because of its ability to measure absorption coefficients. Normal liver tissue has a density of about 1.5 times that of the spleen. Fatty livers are clearly recognizable by their diminished density. A linear relationship exists between the amount of fat in the liver and CT numbers, suggesting that CT may be useful in following therapy. The same linear relationship appears to be true for iron deposition in the liver in thalassemia, Tissue densities higher than normal but lower than those seen in hemosiderosis have been reported in patients who have hepatomegaly due to glycogenstorage disease.14

Computed tomography can help differentiate between obstructive and nonobstructive causes of jaundice, but, since ultrasound depicts dilated bile ducts as well as CT, it is currently preferred for diagnosis of jaundice, especially in the infant, although CT can on occasion yield further information, especially in the older child.

Detection of metastatic disease to the liver seems quite accurate with computed tomography, but studies must be done both with and without contrast for maximal definition. Radionuclide scanning is still the procedure of choice when screening for metastatic liver disease, but if a CT exam is done, for example, for abdominal neuroblastoma and the liver is imaged as part of this examination the radionuclide scan has not been additive. Ultrasound can also identify meta static disease but has been less useful than the radionuclide scan and CT in our experience.

CONCLUSION

The present indications for abdominal computed tomography include assessment of a child with an abdominal mass feared to be malignant, abdominal abscesses, blunt abdominal trauma, and certain parenchymal liver diseases. Computed tomography used properly in these situations will be cost-effective by leading to a correct diagnosis earlier with the use of fewer conventional tests and shorter stays in the hospital.

The dramatic improvements in CT in less than 10 years from its discovery parallels the discovery and development of the roentgen ray itself. Future developments will undoubtedly emerge, but where they will lead us is currently unknown.

REFERENCES

1. Webster, E. W., Alpert, N. M., and Brown ell, G. L. Radiation doses in pediatrie nuclear medicine and diagnostic x-ray procedures. In James, A. E., Wagner, H. M., and Cook, R. E. (eds.): Pediatrie Nuclear Medicine. Philadelphia: W. B. Saunders Company, 1974, pp. 34-58.

2. Seppanen, U., Tomiainen, P., and KiviniitEy, K. Radiation gonad doses received by children in intravenous urography and micturition cystourethrography. Pediatr Radial 8 (1979), 169-172.

3. McCullough, E. C., and Paint, J. Patient dose in computed tomography radiation. Radiology 129 (1978), 457-463.

4. Brasch, R. G., Boyd, D. F., and G coding, C. A. Computed tomographic scanning in children; comparison of radiation dose and resolving power of commercial CT scanners. Am. ]. Roentgenol. 131 (1978), 95-101.

5. Berger, P. E.. Munschauer, R. W., and Kühn, J. P, Computed tomography and ultrasound of renal and peri renai diseases in infants and children: relationship to excretory urography in renal cystic disease, trauma and neoplasm. Pediatr. Radial (In press.)

6. Muhm, J. R., Brown, L. R., and Crowe. J. K. Use of computed tomography in the detection of pulmonary nodules. Mayo Clinic Proc. 52 (1977), 345-348.

7. Hailer, J. O., et al. Left adrenal neuorblastoma with n orma I -appearing urogram. Am- ]. Roentgenol. 129 (1977), 1051-1055.

8. Berger, P. E., Kühn, J. P., and Munschauer, R. W. Computed tomography and ultrasound in the diagnosis and management of neuroblastoma. Radiology 128 (1978), 663-667.

9. Lee, I. K. T., Stanley, R. J., Sagel, 5. S.. and Levitt, R. G. Accuracy of computed tomography in detecting intraabdominal and pelvic adenopathy in lymphoma. Am. }. RoentgenoJ. 131 (1978), 311-315.

10. Callen P. W., Filly, R. A., and Korobkin, M. Computed tomographic evaluation of the diaphragmatic crura. Radiology 126 (1978), 413-416.

11. Berger, P. E., and Kühn, J. P. Computed tomography of tumors of the musculoskeletal system in children: clinkal applications. Radiology 127 (1978), 171-175.

12. Korobkin, M., et al. Comparison of computed tomography, ultrasound, and gallium 67 scanning in evaluation of suspected abdominal abscess. Radiology 129 (1978), 89.

13. Kühn, J. P., Berger, P. E., and Munschauer, R. W. Computed tomographic diagnosis of hidden abdominal abscess in children. Ann. Radial. 23(1980), 153-158.

14. Royal, S. A., Goldberg, H. 1., and Thaler, M. M. Evaluation of childhood cryptogenic hepatomegaly by computed tomography. Paper presented at the 22nd annual meeting, Society for Pediatrie Radiology, March, 1979.

TABLE 1

RADIATION EXPOSURES IN VARIOUS IMAGING PROCEDURES

TABLE 2

COMPARATIVE COSTS OF VARIOUS IMAGING MODALITIES - 1980

TABLE 3

DILUTION OF CONTRAST MATERIAL FOR OPACIFICATION OF SMALL BOWEL AND STOMACH IN PEDIATRIC PATIENTS

TABLE 4

RENALTRAUMA: COMPARISON OF FINDINGS BY INTRAVENOUS PYELOGRAM, ULTRASOUND, AND COMPUTED TOMOGRAPHY IN SEVEN CHILDREN

10.3928/0090-4481-19800501-09

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