Point-of-Care Ultrasound in the Inpatient Setting: A Tale of Four Patients

Renee K. Dversdal, MD; KevinM. Piro, MD; Charles M. LoPresti, MD; Noelle M. Northcutt, MD; Daniel J. Schnobrich, MD

Disclosures

South Med J. 2018;111(7):382-388. 

In This Article

Case 1

A 72-year-old man presented to the hospital with weakness, worsening appetite, and altered mental status. His history was notable for supranuclear palsy, frontotemporal dementia, and chronic urinary retention with suprapubic catheter. His initial vital signs were temperature 37.4°C, heart rate 113, blood pressure 122/81, respiratory rate 18, and blood oxygen saturation 95% on room air. His basic metabolic panel was significant for serum sodium 153 mmol/L, with a reference range (RR) of 136 to 145 mmol/L, serum chloride 119 mmol/L (RR 97–108 mmol/L), and serum creatinine 1.4 mg/dL (baseline 0.7 mg/dL, RR 0.70–1.30 mg/dL). An infectious disease workup was negative. He was admitted to the medicine service, started on 5% dextrose infusion, and fractional sodium excretion was calculated (0.7%).

On morning rounds, repeat laboratory values were notable for a serum sodium of 153 mmol/L and a creatinine of 1.3 mg/dL. The Foley catheter drained appropriately, with 600 mL output overnight. Bedside US was performed, given the absence of improvement in creatinine.

Literature Review and Discussion

Formal renal ultrasound to evaluate for hydronephrosis and renal obstruction is a part of standard acute kidney injury (AKI) evaluation,[8,9] however in the absence of medical history to suggest renal obstruction, formal renal US is a low yield diagnostic modality.[10,11] Formal renal ultrasonography has high sensitivity for hydronephrosis, performs well in the identification of normal kidneys and moderate to severe hydronephrosis,[12] and it has been shown that bedside providers are able to classify hydronephrosis severity with good accuracy.[13] High-quality data regarding the performance of POCUS to identify hydronephrosis in the hospital setting are lacking; however, several emergency POCUS studies serve as validation for the internist-performed examination.[14] Further longitudinal evaluation is warranted because serial examinations may be useful in the setting of AKI, where acute obstructions (within 1–3 days) are less likely to develop hydronephrosis.[15]

POCUS also is useful in volume assessment, a crucial piece of AKI assessment. Inferior vena cava (IVC) assessment has been found to correlate with right atrial pressure (RAP) in spontaneously ventilating patients by evaluating the diameter at the hepatic vein–IVC junction and its degree of respiratory collapse.[16,17] The value is most useful at extremes: dilated and noncollapsible strongly correlate with elevated RAP, whereas a normal to small IVC suggests low to normal RAP.[18] In addition, US assessment of the height of the internal jugular vein meniscus correlates nearly perfectly with internists' physical examination, while also accurately identifying the internal jugular vein in nearly every patient, thus imparting higher confidence in the assessment of elevated RAP.[19] These techniques are learned easily and serial examination of these structures can augment the clinical assessment of intravascular volume.[20,21]

US Findings and Case Resolution

Bedside US demonstrated hyperdynamic left ventricular function, A-line pattern in the lungs bilaterally (no interstitial edema pattern), and an IVC that was <2 cm and collapsed >50% with normal respiration, together suggesting relative hypovolemia (Figure 1). Urinary system US showed bilateral, moderate-to-severe hydronephrosis (Figure 2) and collapsed bladder with visualized Foley. Jugular venous pressure meniscus was below the clavicle with the patient at 30°. The chest x-ray was notable for a sclerotic lesion concerning for malignancy. A prostate-specific antigen test was sent, computed tomography (CT) ordered, and Urology was consulted. Serial POCUS examinations showed worsening of bilateral hydronephrosis, despite repeated flushing of the Foley catheter. Prostate-specific antigen was grossly elevated, and the CT showed bilateral hydronephrosis in addition to multiple axial skeletal lesions.

Figure 1.

Inferior vena cava (IVC). RA, right atrium.

Figure 2.

Dilation of the right renal pelvis and calyces consistent with hydronephrosis. Corresponding ultrasound clips can be viewed at http://links.lww.com/SMJ/A106.

A diagnosis of metastatic prostate cancer was made and hydronephrosis was relieved by ureteral stent placement. The patient was seen by Oncology, started on antiandrogen medications, and discharged with Oncology and Urology follow-ups. A POCUS assessment facilitated a rapid diagnosis of obstructive AKI and streamlined care in a patient with a history that was strongly suggestive of prerenal injury.

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