A 47-year-old woman comes to the office due to fever, dysuria, and abdominal pain. She has had several episodes of urinary tract infections since her teens but no other medical problems. Physical examination reveals mild suprapubic discomfort. Urinalysis shows pyuria and many bacteria. A CT scan of the abdomen is obtained and is shown in the image below. Which of the following most likely prevented the proper ascent of the anomalous organ seen on the CT scan?

Question

A 47-year-old woman comes to the office due to fever, dysuria, and abdominal pain.  She has had several episodes of urinary tract infections since her teens but no other medical problems.  Physical examination reveals mild suprapubic discomfort.  Urinalysis shows pyuria and many bacteria.  A CT scan of the abdomen is obtained and is shown in the image below.  Which of the following most likely prevented the proper ascent of the anomalous organ seen on the CT scan?

Quizplus · Accepted Answer

11ec160b_35dd_27d9_9249_c7db5dcc38a4_MD0001_00 The abdominal CT scan shows the kidneys joined at their lower poles. This is the most common variant of horseshoe kidney, although fusion may also occur at the upper poles. Patients with horseshoe kidney are at increased risk of ureteropelvic junction obstruction, recurrent infection, urolithiasis, and neoplasm (Wilms tumor in children and renal cell cancer in adults). In addition, there is often an aberrant arterial supply to the horseshoe kidney with multiple accessory renal arteries. During kidney development, the embryonic metanephros is initially located in the sacral region. The relative ascent of the kidneys to their normal anatomic position results from the disproportionately rapid growth of the caudal part of the fetus. In adults, the mature kidneys are located at vertebral levels T12-L3. When fusion of the kidneys occurs, the central isthmus of horseshoe kidney crosses the midline anterior to the aorta and posterior to the inferior mesenteric artery (IMA). During fetal development, the IMA limits ascent of the horseshoe kidney. (Choice B) The inferior vena cava lies posterior to the isthmus of a horseshoe kidney and would not obstruct its ascent. (Choice C) A direct connection between the bladder lumen and the outside of the body at the umbilicus is called a persistent urachus or urachal fistula. This condition would likely have been identified earlier in the patient's life. (Choice D) The superior mesenteric artery is located above the inferior mesenteric artery. It leaves the aorta at the level of L1 and does not serve as an obstacle for the ascent of a horseshoe kidney. (Choice E) When the vitelline duct persists, a connection is formed between the intestinal lumen and the outside of the body at the umbilicus. Discharge of meconium from the umbilicus will be seen in this condition. Educational objective: In horseshoe kidney, the kidneys are fused at the poles. The isthmus of the horseshoe kidney usually lies anterior to the aorta and posterior to the inferior mesenteric artery (IMA). During fetal development, the IMA limits the ascent of the horseshoe kidney.

A 47-Year-Old Woman Comes to the Office Due to Fever