Differential Diagnosis for a 15-year-old Female with a 2.6 cm Renal Pelvis

Single Most Likely Diagnosis

• Congenital Ureteropelvic Junction (UPJ) Obstruction: This condition is characterized by an obstruction at the junction where the ureter attaches to the renal pelvis, leading to a dilated renal pelvis. The abrupt transition to the ureter and the presence of a dilated renal pelvis on ultrasound are consistent with this diagnosis. The fact that it is described as a possible mild form of congenital partial obstruction further supports this likelihood.

Other Likely Diagnoses

• Idiopathic Hydronephrosis: This condition involves the dilation of the renal pelvis and calyces without a clear obstructive cause. It could be considered if the obstruction is not significant enough to cause severe symptoms or if the obstruction is intermittent.
• Ureteral Stricture or Kinking: A stricture or kinking of the ureter could cause an obstruction leading to a dilated renal pelvis. However, this would typically be associated with more significant symptoms or a history of trauma, surgery, or infection.

Do Not Miss Diagnoses

• Wilms Tumor or Other Renal Tumors: Although less common, a tumor could cause obstruction of the renal pelvis or ureter, leading to dilation. It is crucial to consider this possibility, especially in pediatric patients, as timely diagnosis significantly affects prognosis and treatment.
• Urolithiasis (Kidney Stones): A stone could obstruct the ureteropelvic junction or the ureter itself, causing dilation of the renal pelvis. This diagnosis is critical to consider due to the potential for severe pain and the need for urgent intervention to prevent long-term kidney damage.

Rare Diagnoses

• Prune Belly Syndrome: A rare congenital disorder characterized by the absence or severe weakness of the abdominal muscles, undescended testes in males, and urinary tract abnormalities, including a dilated renal pelvis and ureters. This condition would typically be identified earlier in life due to its associated physical abnormalities.
• Megacalycosis: A rare non-obstructive condition where the calyces are dilated, but the renal pelvis and ureters are normal. It might be considered if the ultrasound findings are atypical for obstruction and other causes have been ruled out.