Percutaneous Nephrolithotomy in a Patient with Cross-Fused Renal Ectopia

Abstract

Background: Cross-fused renal ectopia (CFRE) is a rare congenital anomaly in which an ectopic kidney crosses the midline and merges with the orthotopic kidney on the other side. Patients with CFRE could present with urolithiasis. The abnormal anatomy and the lack of consensus to treat urolithiasis in these cases present challenges to treatment. In this study, we present a case of renal stone in a CFRE managed through percutaneous nephrolithotomy (PCNL).

Case Presentation: We present a case of a 59-year-old man with right flank pain. Radiologic studies showed a 2 cm renal pelvis stone in a CFRE. The patient was effectively managed with PCNL.

Conclusion: With proper radiologic study and thorough understanding of the aberrant anatomy, PCNL represents a safe and effective treatment for patients with renal stones in CFRE with high stone-free rate and low mortality.

Introduction

Cross-fused renal ectopia (CFRE) is a rare congenital anomaly occurring in 1 in 1000–2000 autopsies, it is the second most frequently observed congenital malformation of the kidney after horseshoe anomaly. In CFRE, both kidneys are located and fused on the same side of the body, with a high incidence of stone formation and urinary tract infection.¹ The lack of consensus in managing stones in CFRE and the abnormal anatomy led to heterogeneous surgical approaches ranging between extracorporeal shock wave lithotripsy (SWL), ureteroscopy (URS), percutaneous nephrolithotomy (PCNL), laparoscopic nephrolithotomy, and even open nephrolithotomy based on surgeon's preference and experience.^1–4

Case Presentation

The patient was a 59-year-old man who was referred to the clinic from a primary health care center with right flank and pelvic pain. Kidney, ureter, and bladder radiograph (KUB) showed a radio-opaque shadow at the right flank (Fig. 1A).

FIG. 1.

(A) KUB radiograph shows a radio-opaque shadow in the right flank. (B) Transverse cut of a noncontrast CT scan shows a stone in the crossed renal ectopia with the renal pelvis facing anteriorly.

Examination

Physical examination revealed a conscious and well-oriented patient with stable vital signs. The abdomen was soft with no abdominal or flank tenderness.

Investigations

Investigations showed white blood cell (WBC) 7.6/L, hemoglobin (Hb) 15.7 g/dL, and creatinine 1.05mg/dL. Urinalysis revealed pH of 6, with occult blood of +2, negative nitrate and red blood cells (RBCs) of 30–40/hpf and WBC of 15–30/hpf.

CT angiogram abdomen and pelvis (Figs. 1B and 2) show right side CFRE, with a left large renal stone measuring 1.4 × 2 cm and HU of 1200 associated with fat stranding and perinephric-free fluid. Three renal arteries and two renal veins are also shown (Figs. 1B and 2).

FIG. 2.

Native CT angiogram shows cross-fused renal ectopia three renal arteries and two renal veins.

Intervention

The patient was consented for bilateral retrograde pyelogram (RGP), bilateral Double-J stent insertion, and PCNL. During the operation, cystoscopy showed bilateral single orthotopic ureteral orifices. Bilateral RGP was performed, which showed a right-sided CFRE. The stone was seen in the crossed kidney (Fig. 3B). There was an acute angle from the left ureteral orifice to the crossed kidney (Fig. 3A). A right ureteral catheter was inserted as a precaution, because the course of the right ureter might be in the PCNL tract. Placement of open tip ureteral catheter was done through the left ureteral orifice to the renal pelvis of the crossed kidney. The patient was shifted to prone position. Puncture through the tip of the posterior lower calix was done as upon the revision of the CT angiogram, there were no major vessels seen, it has the shortest skin to stone distance and it has easy access to the renal pelvis.

FIG. 3.

(A) Intraoperative retrograde pyelograph shows the left ureter traverses a cross-body course to reach the right-sided kidney, which results in an acute angle. A red arrow indicates the ureter. (B) Intraoperative retrograde pyelogram shows contrast in both kidneys. The renal stone could be seen as a filling defect in the cross-fused kidney, indicated by the red arrow.

A super stiff guidewire was then inserted to the level of the bladder. Dilatation up to 28F was done using Amplatz dilators. A 24F nephroscope was inserted. Fragmentation of stone was done using pneumatic lithoclast. Antegrade Double-J stent was inserted. Then an 18F nephrostomy tube was inserted. The procedure lasted 75 minutes (Fig. 4).

FIG. 4.

(A) An intraoperative KUB radiograph. The red arrow indicates the ureter of the crossed kidney with ureteral catheter and a guidewire sliding through it. The blue arrow indicates the Double-J stent in the right kidney. (B) An intraoperative nephrostogram at the end of the procedure showing clearance of the stone and no extravasation.

Postoperative investigations

Postoperative investigations showed WBC 16.2/L, Hb 15 g/dL, and creatinine 1.22mg/dL. Nephrostomy tube was removed on second postoperative day and the patient was discharged in good condition. Double-J stent was removed 2 weeks later by office cystoscopy. The patient was followed up after 3 months. History and physical examination revealed that the patient was fine, with no complaints. Follow-up investigations showed Hb 15.9 g/dL and creatinine 0.78mg/dL. Urinalysis revealed pH of 6 with occult blood Nell, WBCs 0, and RBCs 0. No residual stones seen on KUB.

Discussion

CFRE is a rare congenital anomaly in which an ectopic kidney crosses the midline and merges with the orthotopic kidney on the other side, with two ureters inserted into their normal positions within the bladder trigone.¹ Most patients with CFRE are asymptomatic. Nonetheless, higher susceptibility to urinary tract infections and calculus formation occur in these patients, because of the abnormal anatomic location.¹ The rarity of CFRE and the variant anatomy led to scarce data regarding managing stones in CFRE.³ There was no consensus in the treatment scheme for urolithiasis in CFRE. SWL, URS, PCNL, and laparoscopic nephrolithotomy have been described as a possible effective management of stones in CFRE in case reports.^1–4 In this case, we performed CT angiogram to check for the direction of the renal vasculature to avoid its injury during puncture. The use of Doppler ultrasound-guided puncture could be helpful in such cases especially if CT angiogram shows complex vasculature to avoid traversing these vital vascular structures, if not available a thorough understanding of the vasculature using CT angiogram and careful preoperative planning of the site of the puncture away from major vessels should be carried out (Fig. 2). The major vasculature of the kidney was anterior; the left ureter traverses a cross-body course to reach the right-sided kidney, which results in an acute angle. We deferred from choosing flexible ureteroscopy (fURS) because of the size of the stone (2 × 1.4 cm), the hardness of the stone (HU: 1200), and the acute angle of the ureter that makes it difficult to insert a ureteral access sheath and hence making the clearing of the stone difficult after fragmentation. Utilizing laser dusting technique with fURS is a possible management plan. Nonetheless, we were worried about the possible increase in the intrarenal pressure and the increase in the irrigation temperature without the use of ureteral access sheath. The size of the stone (2 × 1.4 cm) makes it amenable to miniaturized PCNL. Nonetheless, at the time of the procedure, we did not possess the instruments required for this type of procedure.

By the end of the procedure, complete stone removal was achieved. The patient had an uneventful postoperative course. No intraoperative or postoperative complications was encountered.

Conclusion

With a proper radiologic study and thorough understanding of the aberrant anatomy, PCNL represents a safe and effective treatment option for patients with renal stones in CFRE with high stone-free rate and low mortality.

Abbreviations Used

CFRE

cross-fused renal ectopia

CT

computed tomography

SWL

extracorporeal shock wave lithotripsy

fURS

flexible ureteroscopy

Hb

hemoglobin

hpf

high-power field

HU

Hounsfield units

KUB

kidney, ureter, and bladder radiograph

PCNL

percutaneous nephrolithotomy

RBC

red blood cell

RGP

retrograde pyelogram

URS

ureteroscopy

WBC

white blood cell

Disclosure Statement

No competing financial interests exist.

Funding Information

No funding was received for this article.

Cite this article as: Kamal W, Abuzenada M, Almalki A, Alharthi M, Alhazmy A (2020) Percutaneous nephrolithotomy in a patient with cross-fused renal ectopia, Journal of Endourology Case Reports 6:2, 67–69, DOI: 10.1089/cren.2019.0073.