Transperitoneal laparoscopic nephrectomy of non-functional horseshoe kidney that could not be identified preoperatively in a child

Horseshoe kidney is the most common congenital fusion anomaly. Ureters being stuck between the isthmus and the intestines cause urinary stasis and lead to more common development of urinary tract infection and urolithiasis compared to a normal kidney. If not treated, kidney function may be gradually lost. Although the condition is usually diagnosed with ultrasound screening, the diagnosis may be overlooked in patients with a non-functional kidney due to the lack of renal vascularization. We aim to present a 6 years old boy who have non-functioning kidney which is a part of undiagnosed horseshoe kidney. We emphasize that horseshoe kidney should be suspected when live renal parenchyma tissue passing the midline is observed during laparoscopic nephrectomy of a non-functional kidney that could not be preoperatively diagnosed as a horseshoe kidney in this presentation.


INTRODUCTION
Horseshoe kidney is the most common renal fusion anomaly with an incidence of 1 in 400.It is two times more common in males [1,2].The rotation is not full and there is high ureteric insertion point and abnormal course of the ureters the because of its variable blood supply and the presence of an isthmus [3].Urinary drainage may be impaired due to these anomalies and stasis.
Although patients with the horseshoe kidney are usually asymptomatic, they can be found more commonly with urinary tract infection, stone disease, ureteropelvic junction obstruction and renovascular hypertension [4,5].The diagnosis can usually be made with ultrasound screening but the horseshoe kidney may be overlooked when there is a non-functioning kidney without perfusion.
Laparoscopic nephrectomy in the patients with non-functioning kidney is currently preferred due to its advantages such as less post-operative pain, shorter hospitalization duration, small incision and better cosmetic results.We present a patient who underwent laparoscopic nephrectomy of a horseshoe kidney that had become non-functional due to urinary tract infection and could not be diagnosed preoperatively.The laparoscopic treatment approach can be used in anomalous kidneys as a horseshoe kidney [7,8,13].However, it was not possible to make a diagnosis with preoperative investigations in the presented case.We returned to the open surgery method when we saw kidney parenchyma passing the midline during surgery.We encountered with a situation that can not be diagnosed before surgery.Additionally, we had not taken any preliminary measures to avoid the potential complications of partial nephrectomy.

CASE REPORT
In conclusion, the horseshoe kidney

A 6 -
year-old boy patient was referred from another center due to left flank and abdominal pain and intermittent fever.Renal function tests, hemogram and urine culture results were normal.Magnetic resonance imaging (MRI) was taken at another center, the patient was admitted to us with MRI examination, and these images did not show the horseshoe kidney appropriately.The ultrasonography (US) was revealed a markedly hydronephrotic left kidney together with a thin renal parenchyma.The contrast uptake could not be seen in the left kidney.Therefore, the borders of the left kidney could not be distinguished intravenous pyelogram (IVP) in the inspection (Fig. 1).

Fig. 1 .
Fig. 1.IVP: Left kidney contours could not be selected on IVP and no contrast matter was seen in the left renal area.Grade 2 hydronephrosis plus blunt calyxes were also seen in the right kidney.

Fig. 3 .
Fig. 3. Pre-operative right retrograde pyelography: A right retrograde pyelography was performed during the surgery but no pathology explaining the etiology of the right obstruction was seen.As we mentioned before, there was neither ureteral stone nor UPJ obstruction; therefore we concluded as rotational anomaly.

Fig. 4 .
Fig. 4. Isthmus of right kidney and left kidney from which the pre-operative hydronephrosis has been aspirated.
diagnosis can be overlooked due to the lack of renal perfusion during radiological imaging in patients scheduled for surgery with a diagnosis of non-functional kidney.Therefore further examination should be either a contrast enhanced CT or MRI which reveals renal anatomy in detail.It would be useful to consider horseshoe kidney before forcing the tissue when live parenchyma passing the midline is observed during surgery.