Over the past 20 to 30 years, the use of point-of-care ultrasound (POCUS) in clinical care by non-radiologists has greatly increased. As opposed to ultrasounds performed by technicians and reviewed by radiologists, POCUS is less comprehensive and performed in real-time by the providers evaluating the patient. POCUS is focused on answering a clinical question, usually a yes or no question such as “does this patient have gallstones?”. POCUS is now a regular part of residency training in specialties such as obstetrics and gynecology, emergency medicine, and anesthesia.
The growing popularity of POCUS is partially due to advances in ultrasound technology and improved patient care, but also because of increased reports about potential patient harm in chldren with the use of ionizing radiation.1,2 As opposed to radiography (X-ray) or computed tomography (CT), POCUS minimizes radiation exposure. Children are particularly at risk of side effects from radiation and many national campaigns are aimed at attempting to reduce the risks.1–3
In part 14 of this two-part article, we reviewed the use of POCUS for the following clinical scenarios: assessing bladder volume, measuring spleen size, identifying a pneumonia, diagnosing cholelithiasis/cholecystitis, and distinguishing cellulitis from cutaneous abscess. In part 2, we review the use of POCUS for five additional clinical scenarios: (1) helping to diagnose peritonsillar abscess (PTA); (2) hip effusions; (3) assessing fluid status; (4) assisting intravascular placement; and (5) intussusception. The list is not exhaustive, and POCUS applications were chosen based on usefulness, ease of performing, and/or published evidence. The purpose of this article is to make the case for pediatricians to learn more about these POCUS applications and is not meant as a substitute for training on how to execute these studies. The five clinical questions are as discussed in the following text.
Does This Patient Have a Peritonsillar Abscess?
PTAs are the most common deep space infection of the head and neck, with an incidence of 1 case per 10,000 people in the United States.5 Distinguishing a PTA from a severe tonsillitis or tonsillar cellulitis is key because a PTA often requires immediate intervention. PTA is often considered a clinical diagnosis; however, there are often significant limitations in adequate visualization of the posterior oropharynx secondary to trismus, pain, excessive salivation, or a poor mouth opening. Clinical impression is often a poor differentiator of a true abscess versus acute tonsillitis, with only a 78% sensitivity and 50% specificity.6 There are two approaches for evaluating PTA with ultrasound: (1) intraoral using an endocavitary probe or (2) transcervical using a linear high-frequency probe. Both approaches demonstrate high sensitivity and specificity; however, the intraoral approach should be considered the first-line imaging modality if available and if the patient can tolerate it.7
Both approaches have similar efficacy to CT in adults and children, without radiation and with lower cost.8 A PTA on ultrasound will appear as a thick, heterogenous, echotextured wall (tonsillar edema) encapsulating a hypoechoic area (pus or necrotic material) (Figure 1).
Peritonsillar abscess. The arrow is pointing to the peritonsillar abscess, which appears as a thick, heterogenous, echo-textured wall with an encapsulating hypoechoic area.
In a retrospective cohort study, POCUS reduced length of stay, surgical drainage, and radiation exposure from CT scans.9 Only one-third of patients presumed to have PTA by emergency department staff had ultrasound findings consistent with an abscess.9 Not only has POCUS been useful for the diagnosis of PTA, but it has also been shown to improve outcomes when used in real time for the incision and drainage, as blind needle aspiration of a PTA is potentially dangerous with risk of puncturing surrounding vascular structures.10 POCUS for PTAs can aid in diagnosis and disposition of patients, and help a provider decide between surgical drainage versus supportive therapy.
Is That Hip Pain Due to Septic Arthritis?
Hip pain, difficulty with weight-bearing, and a painful limp are common presenting complaints with a broad differential diagnosis. Septic arthritis is one possible etiology that cannot be overlooked given the serious complications that can result if the diagnosis is delayed.11,12 A delayed diagnosis of hip effusion and failure to initiate prompt treatment are the most common causes of late complications of septic arthritis.13 The presence of a joint effusion increases the likelihood of septic arthritis and can facilitate early diagnosis.14,15
Although plain film radiography is useful for detecting osteomyelitis, fractures, or malignancy, its sensitivity for identifying effusions has been reported be as low as 20%.12 Compared to other imaging modalities, ultrasound remains the most sensitive diagnostic tool for detecting even minor pediatric hip effusions.15 A hip effusion appears as a hypoechoic area underneath the hip capsule (Figure 2). In a retrospective review of 154 children admitted to the hospital for suspected septic arthritis, ultrasound was found to be significantly more sensitive for diagnosing a pediatric septic hip compared to clinical, laboratory, and X-ray criteria collectively (P ∼ 0.005).11 Hip effusions are identified with POCUS by readily recognizable sonographic landmarks that can be identified with minimal training.15 One study found that after only 10 practice examinations, pediatric emergency doctors identified hip effusions with a sensitivity of 80% and specificity of 98%.15 It should be noted that the false-negative rate, documented to be as high as 5%, usually involves a patient with symptoms for less than 24 hours and/or who is younger than age 1 year.16
Hip effusion. (A) Arrow shows a hip effusion seen as a hypoechoic area of fluid under the hip capsule. (B) A nonaffected contralateral hip, which shows no fluid under the hip capsule.
Overall, POCUS is a noninvasive, painless, and inexpensive tool that can offer valuable bedside radiographic evidence of a hip effusion and can help expedite subsequent testing for septic arthritis of the hip for a more definitive diagnosis and early management of this time-dependent disease.
Is the Patient's Intravascular Volume Depleted?
The intravascular volume status of children is one of the most common clinical questions that pediatricians face. Unfortunately, individual physical examination findings have limitations. One study reports that even a combination of three or more signs of the 10 commonly elicited signs of dehydration had only a sensitivity of 87% and a specificity of 82%.17 Additionally, laboratory data such as blood urea nitrogen and bicarbonate concentrations can add information, but are only valuable when the results are significantly abnormal and they require painful blood draws.18
Using POCUS to assess a patient's intravascular volume status adds one more tool to the pediatrician's repertoire. Both the ratio of aorta to inferior vena cava (IVC) and the assessment of IVC collapsibility with inspiration have been used to assess hydration status and may correlate with fluid status in children.19 This is particularly true at extremes. Either an IVC with >50% respiratory collapse or an IVC/aorta cross-sectional index <1 indicates significant intravascular volume depletion in a child20 (Figure 3). It has also been suggested that serial POCUS of the IVC can help gauge fluid response.21,22
Inferior vena cava (IVC) measurement. The arrow in both Panel A and Panel B shows the IVC coming off the right atrium (RA). Panel A shows the IVC with inspiration in comparison to the image in Panel B, which shows the IVC with expiration. With inspiration of this patient there is >50% collapse, which signifies hypovolemia.
IVC measurements have been used to estimate central venous pressure (CVP) in adults.23 A combination of IVC diameter and collapsibility can be used to estimate CVP.24,25 For example an IVC with minimal diameter of <20 mm and >50% collapsibility corresponds with CVP ≤5 mm Hg, whereas an IVC of >20 mm minimal diameter and <50% collapsibility corresponds to a CVP of ≥20 mm Hg. POCUS of the IVC can be a significant adjunct in assessing intravascular volume status.
How Can We Obtain Vascular Access When the Blind Approach Is Not Working?
Obtaining prompt intravascular (IV) access is often the first step in stabilizing an acutely sick child in the clinic or hospital. Children who are small, medically complex, or volume-depleted may benefit the most from efficient placement of a vascular line, but these patients also present the greatest challenge in establishing IV access. Numerous studies demonstrate that ultrasound guidance results in faster IV access, reduced number of attempts, and fewer needle redirects in pediatric patients when compared to IV placement using anatomical landmarks.26,27 Properly and timely placed peripheral intravenous catheters avoid the complications associated with central catheter or intraosseous needle access.
POCUS guidance allows the provider to identify the vein, anatomic anomalies, and important surrounding structures such as arteries and nerves. POCUS guidance also allows real-time visualization of the needle passing into the vein during placement.28 In short-axis view, a vein looks like a circle that collapses when compressed (Figure 4). This differs from an artery, which does not compress but that also pulsates. In the long-axis view, the IV catheter can be visualized cannulating the vein in real-time. Ultrasound is becoming a standard tool in obtaining vascular access in children.
Peripheral intravascular (IV) placement. (A) Transverse view of the cross-section of where the IV catheter is going into the vein. (B) Longitudinal view of the IV catheter going into the vein. (Used with permission from Dr. Alexander Prewitt, University of Illinois at Chicago College of Medicine.)
Is This Patient's Abdominal Pain Due to Intussusception?
Intussusception is a pediatric abdominal emergency that needs rapid and accurate diagnosis to prevent ischemic bowel necrosis and perforation leading to serious morbidity and mortality. The longer it takes to make the diagnosis, the higher likelihood of failed nonsurgical intervention.29 Intussusception is a challenging diagnosis to make clinically. Although some children may present with the classic triad of colicky abdominal pain, nausea/vomiting, and currant jelly stools, most do not.
Ultrasound is considered the diagnostic test of choice for intussusception, with an estimated sensitivity and specificity of 97.9% and 97.8%, respectively, and an estimated positive predictive value and negative predictive value of 86.6% and 99.7%, respectively.30 However, ultrasound use can be delayed for hours once diagnosis is considered. Patients often need to be transferred to the emergency department and then evaluated by an emergency provider before the ultrasound is even ordered. Once an ultrasound is ordered, many institutions allow 45 to 60 minutes for a sonology technician, who is often not in house, to arrive before the scan is performed. Making the diagnosis by POCUS has the potential to markedly reduce the time to fluoroscopic reduction and overall length of stay.29 The diagnosis is made by visualization of a target sign, pseudokidney sign, or “crescent in a doughnut” sign (Figure 5).
Intussusception. It appears as a target sign, pseudokidney sign, or crescent in a doughnut sign.
Intussusception can be readily identified even in the hands of a novice sonographer. A prospective observational study reported that even pediatric emergency medicine physicians who are novices to abdominal POCUS had a sensitivity of 85% (95% confidence interval, 54% to 97%) and specificity of 97% (95% confidence interval, 89% to 99%) for evaluating intussusception after a 1-hour training session.31 POCUS is an excellent tool to identify intussusception in real-time and expedite management.
In this two-part article article, we described 10 clinical questions that can be answered at a patient's bedside, in either an inpatient or outpatient setting, using POCUS. There are many other well-studied uses of POCUS in pediatrics, including confirming an intrauterine pregnancy, evaluating for hydronephrosis, deep vein thrombosis, foreign body localization and removal, fracture evaluation, and assessing for increased intracranial pressure. This article is meant to inform and excite the general pediatrician about the potential impact POCUS can make on his or her practice, and to inspire pursuit of further training in these techniques.
We predict that POCUS will have a large role in primary care in the future and can drastically change pediatricians' clinical practice for the better. Imagine a 12-month-old infant who presents to clinic with colicky intermittent abdominal pain. Within minutes, the provider can place an ultrasound probe on the abdomen to assess for intussusception. Similarly, the general pediatrician can assess a 6-month-old's IVC, confirm intravascular volume depletion, and then place a peripheral IV catheter using POCUS right at the bedside.
POCUS provides a wonderful adjunct to physical examination without unnecessary radiation exposure to children. Taking the time to learn POCUS will most certainly result in improved patient care. The applications and innovations of POCUS are changing constantly, with more opportunities to change patient care in daily practice. In our opinion, we feel that if you take the time to learn POCUS, your patients and their families will thank you.
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- Herzon FS, Martin AD. Medical and surgical treatment of peritonsillar, retropharyngeal, and parapharyngeal abscesses. Curr Infect Dis Rep. 2006;8(3):196–202. doi:10.1007/s11908-006-0059-8 [CrossRef] PMID:16643771
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