Bilateral ureterolithiasis: A true positive and false negative PoCUS exam in a patient with renal colic

Abstract

Acute flank pain from suspected urolithiasis is a common presenting complaint in the Emergency Department. Multiple computed tomography (CT) has traditionally been the standard imaging modality used to diagnose obstructive kidney stones, however point of care ultrasound (PoCUS) can play an important role in the diagnostic algorithm and risk stratification of acute flank pain. Here, we present the case of a 29-year-old female with suspected urolithiasis, who underwent PoCUS that revealed right-sided hydronephrosis and normal left kidney, bladder, and aorta. A subsequent KUB was negative. As the clinical course failed to improve with therapy, an abdominal and pelvic CT was ordered revealing a 5 mm distal obstructing ureteric calculus at the right vesico-ureteric junction and another 5 mm left mid ureteric calculus. To the best of our knowledge, this is the first case in which a patient presenting with acute right-sided flank pain demonstrated unilateral hydronephrosis on PoCUS, but had clinically significant bilateral ureteric stones on CT. Emergency physicians who employ PoCUS for evaluation of flank pain must be aware of its benefits and drawbacks and how they apply to each patient. As such, we have developed a script emergency physicians can use for shared decision-making with renal colic patients when deciding on the appropriate imaging modality.

Point-of-Care Ultrasonography in Internal Medicine: Limitations and Pitfalls for Novice Users

“…Also, the examiner needs to be aware of the normal anatomical variations of kidney shape, like the horseshoe kidney and reduplicated renal collecting systems, that they may occasionally encounter. Hydronephrosis can be a surrogate finding in patients with renal stones since not all stones can be seen by ultrasound, but the absence of hydronephrosis does not necessarily mean the absence of stones [64]. Whenever in doubt, the examiner should consider an official ultrasound exam or other radiological modalities to look for such pathologies.…”

Bedside Assessment of the Kidneys and Bladder Using Point of Care Ultrasound

“…Limitations of using hydronephrosis in the diagnosis of renal colic is that a proportion of renal stones do not cause hydronephrosis, and the presence of hydronephrosis does not rule out alternative diagnosis for abdominal pain [38]. Of note, if bilateral hydronephrosis is seen in the investigation of renal colic, other etiologies, associated with a lower urinary tract obstruction, should be considered although simultaneous ureteral obstruction is possible [42]. Patients with renal colic can be severely volume depleted due to associated nausea and vomiting, leading to a false-negative exam for hydronephrosis.…”