Horseshoe Kidney - Erler Zimmer

Horseshoe Kidney - Erler Zimmer

Clinical History

This specimen was discovered during a routine post-mortem examination of a 56-year-old man who succumbed to rheumatic heart disease.

Pathology

The kidney measures 12 cm in length and exhibits fusion at the lower pole, forming a horseshoe-like shape. The ureters emerge from the hilum on the anterior aspect of the 3D print. Horizontal bisection is evident on the posterior aspect, showcasing persistent fetal lobulation. The renal pelvis is notably antero-medially positioned, with the ureters traveling anterior to the fused lower poles or isthmus of the kidney.

Further Information

Horseshoe kidneys represent the most common renal developmental anomaly, occurring twice as frequently in males as in females. They are identified in approximately 1 in 500 to 1000 post-mortem examinations. While most cases are sporadic, some may be associated with chromosomal anomalies, including those leading to Downs and Edwards Syndromes, as well as non-aneuploidic anomalies like VACTERL* association. In 90% of cases, an isthmus of renal tissue connects the lower poles of the kidneys across the midline, forming a horseshoe shape. Fusion of the upper lobes is rare. The renal pelves draining the two halves of the horseshoe kidney are oriented more anteriorly than normal, and there is some ureter angulation as they cross the isthmus.

This malformation is typically asymptomatic and often detected incidentally during routine ultrasound or CT scans. These kidneys generally function normally, but there is an increased incidence of urinary calculi, possibly due to ureter angulation and resulting stasis. A higher risk of hydronephrosis, usually from pelvi-ureteric junction obstruction, is noted. Additionally, there is an elevated incidence of urinary tract infections, primarily due to vesico-ureteric reflux. Some forms of renal malignancies, such as transitional cell carcinoma and Wilms tumors, have also been associated with this anomaly.