Recurrent urinary retention due to clots caused by a congenital renal arteriovenous malformation that forms a complex vascular network: Report of two cases

Acute Abdominal Pain Without Gross Hematuria as an Atypical Initial Presentation of Renal Arteriovenous Malformation

Congenital renal arteriovenous malformations (AVMs) occasionally manifest with recurrent gross hematuria, typically in young populations. Acute abdominal pain without previous episodes of gross hematuria in young women is frequently considered a diagnosis related to obstetric and gynecological conditions or acute appendicitis, excluding the possibility of clot retention, which is more commonly associated with the elderly. A 36-year-old woman with no history of gross hematuria presented with acute lower abdominal pain. Adnexal torsion was initially considered based on her symptoms and ultrasonography findings. However, contrast-enhanced computed tomography (CT) revealed clot retention and delayed contrast excretion in the right kidney. After bladder irrigation, she returned complaining of right flank pain. Subsequent plain CT revealed contrast pooling in the right kidney and hydronephrosis. In addition to these findings, small vessels in the right renal hilum were found to be prominent in the arterial phase on the first contrast-enhanced CT. Finally, angiography of renal arteries confirmed the diagnosis of a congenital cirsoid-type renal AVM, which was successfully treated with ethanol embolization. This case highlights the importance of understanding an atypical presentation of renal AVMs, which is acute abdominal pain, even in the absence of prior gross hematuria and the characteristic CT findings. Early diagnosis of renal AVMs is crucial for preventing potentially serious complications, including repeated clot retention and life-threatening rupture. The diverse clinical manifestations and images of renal AVMs should be recognized to facilitate prompt and accurate diagnosis.