Which condition can present with abdominal/flank pain and be associated with pyelonephritis or hydronephrosis found on ultrasound?

The condition that can present with abdominal or flank pain and is associated with pyelonephritis or hydronephrosis found on ultrasound is vesicourethral reflux. This condition occurs when urine flows backward from the bladder into the ureters and potentially up to the kidneys.

In cases of significant vesicourethral reflux, the backward flow of urine can lead to urinary tract infections, including pyelonephritis, which is an infection of the kidney. Patients may experience abdominal or flank pain as a result of the infection or secondary complications like hydronephrosis, which is the swelling of a kidney due to a build-up of urine. Ultrasound can help visualize the condition by showing kidney enlargement or cumulative fluid, confirming the diagnosis.

Cystitis primarily involves inflammation of the bladder and typically presents with urinary frequency, urgency, and dysuria rather than flank pain or hydronephrosis. Testicular torsion, while presenting with acute scrotal pain, does not involve the urinary tract in the manner described. Nephrotic syndrome involves significant proteinuria and edema but is less directly associated with acute pain and urinary tract infections as seen in vesicourethral reflux. Thus, vesicourethral reflux accurately correl