Kidney stones affect millions of Americans and the prevalence is increasing. Recent literature suggests that the prevalence of stones in the U.S. is 8.8%, with a higher incidence in obese and diabetic patients (Eur Urol 2012; 62:160-5). In the setting of sepsis and ureteral obstruction, urgent decompression is mandatory (J Urol 2013; 189:946-51).
The traditional imaging gold standard to assess for nephrolithiasis is a non-contrast CT scan of the abdomen and pelvis. Verification of an obstructing stone generally requires a dilated ureter leading to an obstructing hyperdense calcification. Confirmation that the calcification lies within the ureter is rarely performed since contrast material would obscure the location of the stone. As a stent is placed care should be taken to visualize the stone, but a small stone can often be missed.
In this particular case, although the patient did have hydroureteronephrosis, the dilated structure containing a calcification turned out to be the dilated appendix. In hindsight, the patient’s right-sided hydronephrosis extended from the mid-ureter at the expected level of the appendix up to the kidney. We believe that the hydronephrosis was secondary to local inflammation from the patient’s underlying perforated appendicitis. As a consequence, while the ureteral stent resolved the patient’s hydronephrosis, it did not address the underlying pathology.
Reassessing the patient was the correct decision. A follow-up CT was warranted for several reasons. First, the patient’s leukocytosis had worsened, suggesting that whatever abscess was present was inadequately drained. Second, a close review of the initial CT shows prompt symmetric pyelograms suggesting minimal obstruction on the right side, which is inconsistent with the working diagnosis of an obstructing ureteral stone. A follow-up CT identified the true diagnosis of acute appendicitis with an accompanying appendicolith masquerading as a ureteral stone.
While flank or abdominal pain associated with hydronephrosis on imaging in conjunction with signs of sepsis should trigger concern for an obstructing calculus, other pathology can present with similar signs and symptoms. Clinicians must keep a critical and discerning eye and an open mind to ensure an accurate diagnosis.
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