Data was obtained and analyzed on 40 individual cases of iatrogenic upper tract foreign body. The majority of retained upper tract foreign bodies (92.5%) were related to a previous urological surgery. The remaining cases of retained material were secondary to previous colorectal, orthopaedic and radiological procedures. Table 1 demonstrates the incidence of retained iatrogenic upper tract foreign bodies and the surgical procedure responsible. The placement of a percutaneous nephrostomy (PCN) and associated percutaneous procedures, account for 35% of all upper tract retained foreign material. Open stone and malignancy surgery – pyelolithotomy, nephrolithotomy and nephrectomy account for 30% of foreign bodies. Cystectomy and continent urinary diversion surgery and endo/ureteroscopic procedures, account for 13.5% of cases. Laparoscopic and open pyeloplasty surgery accounts 8% of upper tract retained foreign material. Colorectal surgery, spinal surgery and radiological interventions account for 7.5% of retained upper tract foreign material.

PCN placement or percutaneous procedures carried out through the nephrostomy tube account for the majority of retained renal foreign bodies. Retained material includes; nephrostomy threads that were inadequately removed from a patient, resulting in stone formation and renal colic. This patient underwent a percutaneous nephrolithotomy (PCNL), were it noted that the threads were encompassed in stone ⁴ (Table 2). Nephrostomy catheters and Malecot nephrostomy tubes have also been retained following PCNL ^{5 6}. A retained Malecot nephrostomy tube, was removed endoscopically, however retained nephrostomy catheters appear be more difficult to remove, requiring percutaneous removal in all cases reported. A portion of a plastic drape bag was also retained following a PCNL. The plastic was inadvertently introduced into the renal pelvis during the procedure, and was later removed by endoscopically ⁷ (Table 3).

The inadvertent catheterization of the renal vein by a PCN tube resulted in the intra-vascular migration of tube. Two cases report independent nephrostomy tube migration into the inferior vena cava, while a third cases reports the presence of a nephrostomy tube in the right atrium ^{8 9}. Successful removal of the foreign bodies was achieved by interventional radiology. The final case of a foreign body related to PCNL is that of an Amplatz sheath that inadvertently migrated out of the renal pelvis into the peritoneal cavity. This necessitated a laparoscopic approach for removal ¹⁰.

Open stone surgery accounts for approximately one third of all iatrogenic renal foreign bodies. The most common object retained is suture material or gossypiboma (Table 1). Silk sutures are the most commonly reported material retained. Polyglactin (vicryl); an absorbable suture was the second most common retained suture. Retained sutures can act as a nidus for stone formation, and in the majority of cases, patients presented years after the initial procedure with renal colic ^{11 12 13}. Endoscopic destruction of the stone has been reported to be successful ^{11 12}, however severe stone burden may necessitate open surgery ¹³ (Table 2).

One patient with retained suture material following a pyelolithotomy represented with haematuria 8 years after the initial procedure. A CT Urogram demonstrated a renal mass; and the patient underwent a laparoscopic nephrectomy, histological analysis demonstrated no malignancy and only granuloma formation around retained suture material ¹⁴ (Table 4). Similarly gossypiboma can incite an inflammatory reaction similar to that of the above case, which has the appearance of a renal or retroperitoneal tumour on imaging ¹⁵. There are 7 reports of gossypiboma following open renal surgery, in every case the gossypiboma was misdiagnosed preoperatively as a renal or retroperitoneal malignancy. Subsequently all of these patients underwent major surgery and 85% of these patients had a radical nephrectomy ^{15 16 17 18 19 20} (Table 4).

Endoscopic surgery for urolithiasis has resulted in five cases of retained renal foreign body. It is ironic that instruments used to treat stone disease lead to further stone formation in 80% of cases highlighted in Table 2. Retained endoscopic equipment includes, 2 cases of retained laser fiber wire, 2 cases of fractured guide wires and 1 case of a piece of ureterorenoscope that broke off intra-operatively ^{21 22 23 24} (Table 1). The majority of cases were managed endoscopically ²² , however a fractured guide wire ²³ and the part of the ureterorenoscope needed PCN removal due to associated stone burden ²⁴ (Table 2).

Iatrogenic renal foreign bodies after an ileal conduit or urinary diversion are related to gastrointestinal anastomosis (GIA) clips refluxing into the renal collecting system. The presence of a GIA clip in the collecting system again acts a nidus for stone formation has been frequently reported ^{25 26 27 28 29}. Ureterorenoscopic treatment of the stone and the refluxed staple has been reported ²⁵, however it is more likely that a percutaneous approach would be favored especially in the setting of heavy stone burden (Table 2).

Retained foreign bodies post open or laparoscopic pyeloplasty are infrequent. Nevertheless retained material reported includes a Hem-o-lok clip, surgical clip and suture material (Table 1). The Hem-o-lock clip migrated into the collecting system leading to stone formation. Endoscopic management was unsuccessful and the patient required PCN for removal of the clip and the associated stone burden ³⁰. In addition, intra-renal clips post pyeloplasty have required PCNL for treatment ³¹. Retained polyglactin (vicryl) sutures and associated calculi were successfully removed by an endoscopic procedure ³² (Table 2).

Retained suture material has also been reported following a subtotal colectomy, where the suture migrated into the collecting system. In this case, the retained suture lead to stone formation, this calculus was not amenable to endoscopic removal and needed a PCNL for removal ³³ (Table 2). The erosion of radiological embolisation coil from the renal artery into the renal pelvis has also been reported. The patient initially underwent selective embolisation following a renal haemorrhage related to PCN insertion. However, several years later the patient presented with flank pain and was diagnosed with an intra-renal embolisation coil and associated stone formation. This was successfully managed non operatively, and the patient passed the foreign body spontaneously ³⁴. A spinal procedure has also resulted in final and most unusual case of renal foreign body. The patient in question underwent a procedure in which a myelography needle was inserted in their spine. The needle was lost during the procedure. Over the course of several years the progress of the needle was monitored by serial imaging, eventually the needle eroded into the renal pelvis. The patient did not require operative management ³⁵ (Table 3).

Figure 1

Table 1: Incidence of upper tract iatrogenic foreign bodies and original procedures

Tabulated summary of all renal iatrogenic foreign bodies according to original procedure responsible, type of foreign body, number of reported cases.

PCN, Percutaneous nephrostomy; PCNL, Percutaneous nephrolithotomy

Figure 2

Table 2: Management of upper tract foreign bodies that developed associated stone formation

Tabulated summary of cases series reporting management of retained encrusted upper tract foreign bodies, with the number of individual cases and management approaches.

PCN, Percutaneous nephrostomy; PCNL, Percutaneous nephrolithotomy

Figure 3

Table 3: Management of additional upper tract foreign bodies

Tabulated summary of cases series reporting management of retained upper tract foreign bodies that did not have stone encrustation, with the number of individual cases and management approaches.

PCN, Percutaneous nephrostomy; PCNL, Percutaneous nephrolithotomy

Figure 4

Table 4: Management of upper tract foreign bodies that were mistaken for a malignancy and outcome

Summary of cases series reporting management of retained upper tract foreign bodies that were mistaken for renal or para-renal neoplasms. Results tabulated according to original procedure responsible, type of foreign body, presentation, interval to presentation appearance on radiological imaging and outcome.