Variant Anatomy in Women with Horseshoe Kidney Can Make Pelvic Reconstruction Challenging

Horseshoe kidney (HSK), a congenital condition, is the most common fusion defect of the kidneys. Patients with an HSK are at increased risk of recurrent urinary tract infections, kidney stones, common kidney cancers and some very rare cancers such as a carcinoid tumor. It's characterized by abnormalities in the position, rotation and vascular supply of the kidney. As a result there can be an abnormal position of the renal pelvis and ureters, as well as variant arterial supply and venous drainage.

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Milena M. Weinstein, MD, a specialist in the Female Pelvic Medicine and Reconstructive Surgery Program at Massachusetts General Hospital, Marcus V. Ortega, MD, a fellow, and colleagues have found that HSK has implications for gynecologic surgeons. In Female Pelvic Medicine & Reconstructive Surgery, they report variation in major vascular and urinary structures near the presacral space that can affect the feasibility of minimally invasive pelvic reconstruction.

Study Details

Using a large database for Mass General and its partner hospitals, the researchers identified 20 women with an HSK who were imaged between August 1988 and December 2018 and had no other renal anomalies. These women also had an interpretable multiplanar computed tomography or MRI scan available.

The images were reviewed independently by two radiologists. Relevant anatomy was compared with normal female anatomic measurements published in radiographic and cadaveric studies.

Measurements and Implications for Surgery

Aorta and vena cava: Women with an HSK had a narrower aortic bifurcation angle than controls (39° vs. 52°; P = .01), and the bifurcation of the vena cava was more likely to be below the level of L5 (40% vs. 8%; P < .001). Thus, the iliac vessels could be closer to the sacral promontory, and dissection of the sacral promontory might not be safely achievable.

Ureter: The right ureter was significantly closer to the midline of the sacral promontory in women with an HSK compared with controls (23 vs. 32 mm; P < .001). Small variations in the distance between the right ureter and the area of dissection along the sacral promontory can be critical to avoid ureteral injury during sacrocolpopexy.

Kidney position: In 95% of women with an HSK, the inferior pole of the centrally fused kidney was below the expected level of L3, and in 15% of women, it was at the level of S1. This location might further compromise safe dissection of the presacral space, precluding suture placement into the anterior longitudinal ligament.

General Advice About HSK & Pelvic Surgery

The researchers give the following advice:

• Established diagnosis of HSK - Preoperative imaging is advised to identify the proximity of the kidney to the sacral promontory
• If HSK is present but unknown prior to sacrocolpopexy - The surgeon may encounter a presacral mass at the sacral promontory. Suggestions in such cases are to abort the use of the promontory as a point of attachment and consider either dissection below the promontory or another pelvic reconstructive approach
• If HSK is discovered incidentally intraoperatively - The surgeon should perform retrograde urography to assess the exact course of the ureters and location of the renal pelvises. Use best judgment about whether to pursue alternative surgical options such as suture suspensions performed abdominally or vaginally

Conclusion

Women with HSK who have anatomic alterations makes surgical interventions challenging. Preoperative imaging is recommended to determine the feasibility of reconstructive surgery.

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