Renoalimentary Fistula 

Updated: Jan 06, 2021
Author: M Francesca Monn, MD; Chief Editor: Edward David Kim, MD, FACS 



Fistulae between the upper urinary tract and the GI systems are rare. Iatrogenic injury is the most common etiology of renoalimentary fistula, although various pathologic processes in either organ system may lead to fistulization.[1] Most renoalimentary fistulae are iatrogenic, secondary to percutaneous nephrostomy tube placement, although penetrating and blunt trauma, malignancy (particularly colon, renal, and transitional cell cancer), foreign body ingestion, and inflammatory processes (usually secondary to stones, infection, or diverticular disease) are occasionally implicated in renoalimentary fistulae.

Renoalimentary fistula has also been reported as a complication of percutaneous radiofrequency ablation and laparoscopic cryoablation. As more patients with small renal tumors are now undergoing these advanced forms of tumor treatment, surgeons should be mindful of renoalimentary fistula as a potential complication of them.[2, 3, 4]

If recognized early, many iatrogenic renoalimentary fistulae may be treated conservatively, eliminating the need for surgery. Chronic renoalimentary fistulae are more likely to require surgery.

History of the Procedure

Hippocrates is credited for the first reported case of renoalimentary fistula in 460 BC. Renoalimentary fistulae began to be recognized more commonly in the mid 1800s and were predominantly due to renal tuberculosis (TB). A distant second cause was pyelonephritis due to infection with other organisms.[5, 6] With the exception of pyelonephritis in conjunction with stone disease, infectious causes of renoalimentary fistula diminished with advancements in antitubercular and antimicrobial therapy. As a result, renoalimentary fistulae became much less common between 1950 and 1980, with malignancy being the primary etiology.

With the advent of minimally invasive renal surgery, the incidence of renoalimentary fistulae, specifically iatrogenic renoalimentary fistula, has increased. Despite the increase, this phenomenon remains quite rare.


Renoalimentary fistulae may involve any portion of the GI tract that has an abnormal connection with the kidney. The resulting drainage of urine into the GI tract, GI contents into the urinary tract, or both can lead to diarrhea, urinary tract infections, and various electrolyte abnormalities.



Renoalimentary fistulae comprise fewer than 1% of fistulae between the urinary and intestinal tracts, the vast majority of which are colovesical fistulae.


Most renoalimentary fistulae are iatrogenic, secondary to percutaneous nephrostomy tube placement, percutaneous radiofrequency ablation, or laparoscopic cryoablation. Trauma, foreign body ingestion, malignancy (particularly colon, renal, and transitional cell cancer), and inflammatory processes (usually secondary to stones, infection, or diverticular disease) have also been implicated in some cases.

The kidneys and their associated structures are normally separated from the enteric system by the peritoneum, Gerota fascia, and perirenal fat. Consequently, renoalimentary fistulae tend to occur where these structures are manipulated, attenuated, or absent. Fistulization between the renal collecting system and the gut is more common in individuals who are thin or who are nutritionally debilitated. Renoalimentary fistulae are also more likely to develop in patients who have undergone renal surgery.

Renocolic fistulae are the most common type of renoalimentary fistulae.


All of the following have been implicated in renoalimentary fistulae:

A case report has described a sinus tract between the appendix and renal collecting system secondary to appendicitis.[10]

The most common iatrogenic cause of renoalimentary fistula is the inadvertent placement of a percutaneous nephrostomy tube through the colon. Generally, this occurs because the colon is posteriorly displaced and may even contain a retrorenal component. This anomalous anatomy is more common on the left than the right and is seen more frequently in females than in males. A retrorenal colon is more commonly encountered at the caudal aspect of the kidney.

Fistulae following radiofrequency ablation or cryoablation are likely secondary to unrecognized bowel injury (colon or duodenum) in close approximation to the lesion being treated and are usually not discovered until follow-up imaging is performed unless they become clinically symptomatic (see CT image below). Tumor recurrence may also play a role in fistula formation following therapy.

CT scan of an apparent colorenal fistula following CT scan of an apparent colorenal fistula following radiofrequency ablation of a small right renal tumor in a 51-year-old man. Air was found within the collecting system. Conservative treatment of the fistula was successful.

Another common iatrogenic cause of renoalimentary fistulae is the breakdown of anastomotic suture lines when renal and bowel surgery are performed simultaneously. Such procedures are commonly used to treat locally advanced transitional cell carcinoma of the bladder or ureter that requires intestinal interposition for urinary diversion. Patients with neurogenic bladder dysfunction or congenital abnormalities of the urinary tract may also undergo intestinal reconstruction and be at risk for fistula formation. See images below.

Renoalimentary fistula. A 61-year-old patient with Renoalimentary fistula. A 61-year-old patient with a history of urinary diversion due to transitional cell carcinoma of the bladder presented with back pain and underwent a bone scan to evaluate for the presence of metastases. Bone scan findings revealed drainage of the urinary radioisotope into the colon.
Renoalimentary fistula. A 61-year-old patient with Renoalimentary fistula. A 61-year-old patient with a history of urinary diversion due to transitional cell carcinoma of the bladder presented with back pain and underwent a bone scan to evaluate for the presence of metastases. Bone scan findings revealed drainage of the urinary radioisotope into the colon (same patient as in the image above). Subsequent intravenous pyelography revealed contrast in the renal pelvis draining into the colon on the right.

Ingestion of a foreign body is most likely to lead to a pyeloduodenal fistula as a result of the foreign object lodging in the duodenum with resultant inflammatory reaction that involves the duodenum and posteriorly adjacent renal pelvis.

Cutaneous extension of the fistula is reported in 10% of cases.


The clinical presentation of a patient with a renoalimentary fistula varies. Patients may present with isolated abdominal or flank pain with fever. However, in many cases, fecaluria, hematuria, pneumaturia, biliuria, dysuria, recurrent urinary tract infection (UTI), or watery diarrhea may be present. There have been reports of patients presenting with bloody diarrhea, with resultant pallor and fatigue, particularly in the setting of concurrent malignancy.[11, 12]  Evidence of sepsis with fever and leukocytosis is common. The presence of peritoneal signs may necesitate immediate surgical exploration.

When caused by percutaneous nephrostomy tube placement, gas and enteric contents may drain through the nephrostomy tube, while voided urine may or may not appear normal.

Renoalimentary fistulae due to radiofrequency ablation or cryoablation have been discovered on routine follow-up imaging and have been mostly asymptomatic.[3, 13, 14]

There have been multiple reports of renoalimentary fistulae arising from chronic inflammatory processes such as xanthogranulomatous pyelonephritis.[15]  Staghorn calculi are the classic renal stones that have been identified as origins of xanthogranulomatous pyelonephritis, leading to the possibility of a fistula.[15]  Malignancies may also cause a fistula to form, most commonly colorectal and renal cell carcinomas.[11]

Physical examination findings in patients with renoalimentary fistulae tend to be fairly nonspecific. Patients may be febrile and have noticeable signs of anemia due to the loss of blood in the stool/urine, such as pallor. Flank fullness may be found on the side of the affected kidney, and the affected kidney can be firm and non-tender. In many cases, abdominal tenderness or pain is present; however, it may not be localized. Costovertebral angle tenderness may also be noted.


If peritonitis is present, immediate surgical exploration is mandated. If the patient is stable, elective resection of the fistula following mechanical and antibiotic bowel preparation is preferred.

An exception is renoalimentary fistulae caused by iatrogenic injury to the bowel during percutaneous nephrostomy placement. If the injury is recognized early and the patient does not display signs of peritonitis, the accepted treatment is to pull back the percutaneous tube so that it drains the renal pelvis without maintaining the fistulous connection with the colon. Conservative management has been successful in asymptomatic renoalimentary fistulae following minimally invasive procedures.

Relevant Anatomy

The kidneys are paired retroperitoneal structures with several layers of investing tissue planes that separate them from the peritoneal contents. The retroperitoneal colonic segments are usually anterior to the kidneys, and the duodenum abuts the right kidney medially and anteriorly, rendering these bowel segments susceptible to fistula formation within the kidney. Renoduodenal fistulae mostly involve the descending part of the duodenum because of its relative immobility, lack of a posterior peritoneal covering, and close contact with the anterior kidney.[16, 17, 18]


Patients with renoalimentary fistulae due to cancer may not heal and may develop further complications such as systemic sepsis, severe electrolyte abnormalities, and even death. The ability to completely resect the tumor at the site of the fistula is a key element to success.

If the patient is severely malnourished, the chance of successful repair is decreased significantly. If the patient is not acutely ill from the fistula, repair should be delayed until nutritional status improves. Bowel rest and parenteral nutrition may be necessary to accomplish this goal, particularly if the patient has a gastric or small-intestine fistula.


The prognosis of a patient with a renoalimentary fistula depend largely on its etiology and duration, and on the patient's general health. If xanthogranulomatous pyelonephritis is the source of the fistula, then the prognosis relies on early diagnosis and management of the pyeloneprhitis.[15]  If associated with a malignancy, then the most important factors for prognosis are tumor grade and stage.[12]




Left untreated, clinicians can expect to see worsening symptoms of the fistulae. Anemia, urinary tract infections, sepsis, declining renal function, and worsening gastrointestinal and voiding issues are all potential outcomes of untreated fistulae[19] .



Diagnostic Considerations

Identification of a renoalimentary fistula is largely based on diagnostic imaging and procedures.  Cross sectional imaging demonstrating air in the urinary tract with bowel closely approximating the renal collecting system, particularly after recent surgical interventions (such as percutaneous nephrolithotomy or radiofrequency ablation of renal tumors) or in the setting of xanthogranulomatous pyelonephritis, and without other reasons for its presence should prompt consideration of this rare fistula.

Underlying causes should be located or ruled out as renoalimentary fistulae are relatively rare. Spontaneous renoalimentary fistula that are not associated with iatrogenic causes tend to commonly be associated with primary bowel pathologies such as inflammatory bowel disease or malignancies. In the absence of a primary bowel pathology or possible iatrogenic cause, a diagnosis of renoalimentary fistula is less likely[15] .

Differential Diagnoses

  • Entero-vesical fistula

  • Pyelonephritis

  • Uretero-intestinal fistula



Laboratory Studies

Laboratory studies in patients with possible renoalimentary fistula include the following:

  • Complete blood cell count with differential – May provide evidence of sepsis

  • Serum electrolytes – The loss of alimentary contents through the fistula may lead to electrolyte abnormalities

  • Serum kidney function tests – Blood urea nitrogen (BUN) and creatinine values may help determine the degree of renal insufficiency, if any

  • Urine culture – Particularly with colonic fistula, bacteria in the urinary tract can result in urosepsis with any manipulation; if any predominant urinary pathogen is present on urine culture results or if fungal overgrowth due to prolonged antibiotic administration is present, directed therapy can be instituted

  • Tuberculosis (TB) skin testing, along with the collection of three early-morning first-void specimens for urine acid-fast bacilli (AFB) culture, are used to evaluate for TB when no other source is readily evident.

Imaging Studies

Renoalimentary fistulae may be diagnosed with the aid of either renal or alimentary imaging studies. The predominant direction of flow tends to be from the urinary tract to the GI tract, and renal imaging tends to reveal the lesions most often.

Renal imaging

Intravenous urography (IVU) may help identify the fistula. In chronic cases of renoalimentary fistulae, the kidney is often functioning poorly, which limits the value of performing an IVU.

Retrograde pyelography can often help establish the diagnosis and help define the exact location of the fistula within the upper urinary tract. In this procedure, which is performed under cystoscopic and fluoroscopic guidance, a catheter is introduced into the ureteral orifice and contrast is injected. The catheter can be advanced farther into the area under investigation, and more contrast can be injected to help confirm the diagnosis; however, extensive manipulation is discouraged because it may cause perforation or urinary sepsis. The configuration of the contrast in the bowel also may help identify the intestinal segment involved.

Cystoscopic examination of the bladder and ureteroscopic examination of the upper urinary tract can be performed while the patient is under anesthesia for retrograde pyelography. This is performed to help rule out urinary tract malignancy as an etiology.

Retrograde pyelography may fail to opacify small fistulae or to demonstrate fistulae proximal to an obstructing proximal ureteral calculus, which prevents passage of contrast into the proximal collecting system where the fistulous connection may be located. This study may be difficult to perform secondary to inflammatory changes of the bladder, preventing identification and cannulization of the ureteral orifice.

GI tract imaging

Upper GI series are useful for diagnosing renoalimentary fistulae potentially involving the duodenum or small bowel.

Barium enemas may be used to identify large bowel fistulae. A Gastrografin enema is usually preferable to a barium enema when a urinary fistula is expected because barium can cause obstruction and serve as a nidus for stone formation. However, the relative density of barium in comparison to urine allows the examiner to perform the Bourne test.

The Bourne test is performed when a fistula may be present between the colon and the urinary tract but the barium enema findings are not diagnostic. Urine is collected after the barium enema is performed and then centrifuged. If radiography of the centrifuge tube shows opacity due to barium, a connection between the urinary tract and the colon must be present. Care must be taken, especially in women, to avoid any contamination of the urine sample to be centrifuged with barium washed off the perineum during voiding.

Complete imaging and endoscopy of the GI tract are necessary in cases of spontaneous renoalimentary fistulae in order to rule out GI malignancy as an etiology.

CT scan and radiography

CT scanning is probably the most helpful study for discerning the underlying pathology of the renoalimentary fistulae, such as xanthogranulomatous pyelonephritis (XGP) or an abscess. CT scanning is routinely used to monitor treatment outcomes following radiofrequency ablation or cryoablation.

Findings from a plain film of the abdomen occasionally demonstrate air in the collecting system, but CT scanning yields better sensitivity for this finding. Free air under the diaphragm on plain films in a patient who has not undergone recent surgery may suggest a more extensive bowel defect and may indicate the need for more immediate surgical intervention.

Chest radiography can be helpful for detecting cardiopulmonary disease, which may influence intraoperative management, and is necessary for staging if the fistula is due to malignancy.

Nuclear imaging

Nuclear kidney scan findings may show that the affected kidney is not functioning, particularly in cases of XGP. If the affected kidney is not functioning, less complicated surgical approaches can be used, including simple nephrectomy and bowel repair rather than repair of both the intestinal and urinary component of the fistula.

Very small fistulae, which are difficult to localize using the standard methods mentioned above, may be made more evident with oral administration of an isotope or intravenous administration of isotopes concentrated in the urine followed by nuclear imaging of the abdomen. See images below.

Renoalimentary fistula. A 61-year-old patient with Renoalimentary fistula. A 61-year-old patient with a history of urinary diversion due to transitional cell carcinoma of the bladder presented with back pain and underwent a bone scan to evaluate for the presence of metastases. Bone scan findings revealed drainage of the urinary radioisotope into the colon.
Renoalimentary fistula. A 61-year-old patient with Renoalimentary fistula. A 61-year-old patient with a history of urinary diversion due to transitional cell carcinoma of the bladder presented with back pain and underwent a bone scan to evaluate for the presence of metastases. Bone scan findings revealed drainage of the urinary radioisotope into the colon (same patient as in the image above). Subsequent intravenous pyelography revealed contrast in the renal pelvis draining into the colon on the right.

Antegrade pyelography

Features of antegrade pyelography include the following:

  • Helps to reveal fistulae not visualized via retrograde pyelography
  • Allows intrarenal sampling of urine
  • The drainage catheter can be placed before or after completion

Other Tests

Oral agents

Proof of more elusive fistulae can be obtained by administering an oral dye that is not absorbed into the blood stream and monitoring the urine for color change.

Oral administration of finely powdered carbon particles over several days followed by daily collection of urine, which is then centrifuged and examined microscopically, can occasionally demonstrate fistulae that are only patent periodically. This type of fistula is occasionally seen in patients who are on bowel rest or have inflammatory conditions of the bowel that have responded well to medical treatment.


ECG findings can provide information about any underlying cardiovascular disease that may influence intraoperative management. Performing an ECG is particularly important if intestinal losses or renal insufficiency is causing electrolyte abnormalities.


Perform cystoscopy in cases of pneumaturia and dysuria to help rule out the more common vesicoenteric fistula. Cystoscopy may show that air or intestinal contents are draining through the ureteral orifice on the affected side or may reveal evidence of bladder malignancy. The inflammatory reaction and edema associated with chronic urinary infection may preclude visualization of the ureteral orifices.

Ureteroscopy or percutaneous nephroscopy is more invasive and may expand the size of the fistula or cause urosepsis. However, these imaging techniques can allow direct visualization of the fistula tract, and findings can be diagnostic if upper tract transitional cell carcinoma is present.

Upper and lower GI endoscopy should be performed when the cause of the fistula is unknown. This procedure helps evaluate for the presence of GI malignancy or inflammatory bowel conditions.

Histologic Findings

Findings depend on the underlying pathology. For example, fistulization secondary to an abscess reveals neutrophilic infiltration and the presence of bacteria. Similarly, XGP might be associated with the presence of pathognomonic foamy macrophages. Cancer, usually a GI malignancy or extensive renal cell carcinoma, shows involvement of the tumor, which may be subtle if abundant surrounding inflammation is present.



Medical Therapy

Antibiotic therapy is instituted to assist in the treatment of concomitant infection, but surgical intervention remains the definitive treatment for renoalimentary fistulae.[20]

In rare cases, a fistula between the intestinal and urinary tracts due to inflammatory bowel disease resolves with aggressive medical therapy (anti-inflammatory agents and steroid therapy) of the inflammatory process.

In high–surgical-risk patients, a few case reports have described success with conservative management that consisted of prolonged percutaneous drainage along with a low-residue diet, in cases of inflammatory etiology.

In the rare cases of renoalimentary fistula following radiofrequency ablation or cryoablation, conservative measures have been successful.[3]

Surgical Therapy

The choice of surgical therapies largely depends on the etiology of the fistula and the segment of bowel involved. Generally, surgical therapy involves resection of the involved bowel segment, reanastomosis, and resection of the fistula tract to the kidney. If kidney function is severely compromised (ie, inadequate to maintain the patient without dialysis in the absence of the contralateral kidney), a nephrectomy may be more efficacious than attempts at repairing the urinary tract component of the fistula.

Fistulae that occur from benign inflammatory causes (eg, xanthogranulomatous pyelonephritis) should be treated with nephrectomy and bowel diversion vs resection, as indicated.[21]  However, malignant fistulae from metastasis should be treated as locally advanced tumors with en bloc resection if feasible.[12]

Successful percutaneous fulguration of the fistula tract has been described in a case report and may be an option when the fistula is caused by longstanding calculi and abscess after removal of the calculus and drainage of abscess in patients who are not candidates for more aggressive surgical intervention.[22, 23]

Successful CT-guided and endoscopic fistula repair has also been reported in a case report due to the patient being a poor candidate for surgical treatment.[24]

Preoperative Details

Obtain a history and perform a physical examination to evaluate for any increased surgical risks, including allergies. Patients should give consent for all possible surgical permutations required to repair the renoalimentary fistula, including nephrectomy (which may result in renal failure and possible dialysis), urinary diversion, intestinal diversion, and prolonged hospitalization with bowel rest and parenteral nutrition. The patient also may die, and this should be addressed during the consent process.

Complete blood cell count, electrolyte evaluation, kidney function studies, urine culture, chest radiography, and ECG should be performed as described in Workup.

Mechanical bowel preparation consists of 2-3 days of a clear liquid diet and cathartics that do not result in excessive electrolyte imbalance (eg, polyethylene glycol & electrolytes [1 L of Go-Lytely]). Patients who have been on prolonged bowel rest may not need this aggressive cleansing approach. Antibiotic bowel preparation with oral neomycin (500 mg) and erythromycin base (1 g) can be considered. Patients with diabetes or those who are immunocompromised may benefit from prophylactic oral rinses with antifungal agents and antifungal powder, such as nystatin in the intertriginous areas to prevent yeast overgrowth while undergoing bowel preparation and in the immediate postoperative period.

Patients on long-term steroid therapy to treat inflammatory bowel disease or other ailments should receive stress-dose steroid therapy perioperatively. Typically, this regimen consists of 100 mg hydrocortisone preoperatively and 100 mg/d for 3 days, followed by a tapered reduction in dose until the patient's standard steroid dosing schedule is reached.

Broad-spectrum antibiotics targeting both bowel flora and common urinary tract pathogens should be administered least 1 hour preoperatively and 1 day postoperatively. A longer duration of therapy may be necessary in patients with infectious complications of the fistula.

Intraoperative Details

An anterior subcostal or midline transperitoneal incision is well suited because either allows easy exposure to the kidney and bowel. Pyeloduodenal fistulae may be accessed through retroperitoneal exposure alone. In addition to open surgical approaches, transperitoneal hand-assisted laparoscopic approach for exposure to bowel and kidney has been reported with success.

If the kidney is salvageable, repair may be possible, although bowel resection and reanastomosis are often required. This involves excision of the fistula complex, including the affected bowel and urinary tract segment, followed by repair of the kidney and/or ureter and reanastomosis and/or diversion of the bowel. If urinary stone disease is an etiology or secondary complication of the fistula, all stones should be cleared from the collecting system.

A stent or nephrostomy tube should be left in the kidney and a nasogastric tube in the stomach to prevent stressing of the anastomotic suture lines in the immediate postoperative period. A urethral catheter should also be placed. To help prevent fistula recurrence, interposing the omentum or other viable tissue is important.

If the kidney is not functioning, a nephrectomy is indicated.

Intraperitoneal suction drains, such as a Jackson-Pratt drain, should be left in place to avoid life-threatening sepsis should the repairs fail.

Postoperative Details

Bowel sounds, passage of flatus, and an appetite should all be present before attempting oral nutrition. A clear liquid diet should be initiated slowly and advanced to a regular low-residue diet if well tolerated and if no intestinal contents are appreciated in the urinary or intraperitoneal drains. The urethral catheter can be removed as the diet is successfully advanced.

Although the absence of continued symptoms is an encouraging sign of successful repair, nephrostography or retrograde pyelography should be performed 4-6 weeks postoperatively. If no persistence or recurrence of communication is present, the stent and/or nephrostomy tube can be removed. If the urinary repair is at all tenuous, the intraperitoneal drains should be left in place until all urinary stents and drainage tubes are removed. If no urinary output is present once all tubes are removed, the drains can be removed.


Appropriate radiographic and laboratory follow-up studies should be performed as mandated by the histology and stage of malignancy for patients with renoalimentary fistulae occurring secondary to tumors. Fistulae due to calculi should prompt a metabolic evaluation and follow-up imaging with a plain abdominal film in approximately 6 months, or, if the patient develops any symptoms, intravenous urography or a noncontrast CT scan should be performed.

Intravenous pyelography or another functional study for fistulae from other benign causes should be performed 3-6 months after repair to confirm stable kidney function and adequate kidney drainage.


Anastomotic breakdown of the bowel, bowel or urinary tract obstruction, abscess recurrence, or formation and recurrence of the fistula (when the kidney is salvageable), sepsis, and even death are all possible complications of this type of surgery.

The following measures are all crucial to minimize the risk of complications:

  • Complete resection of the fistula and any associated abscess cavity, necrotic tissue, inflammatory mass, tumor, stones, or foreign bodies
  • Perioperative antibiotics
  • Tension-free closure of both the bowel and urinary components
  • Interposition of healthy tissue, such as omentum
  • Copious would irrigation
  • Drain placement
  • Adequate nutritional support 

If postoperative complications develop, one or more of the following may be necessary:

  • Surgical exploration
  • Percutaneous drain placement
  • Nephrostomy tube placement
  • Prolonged bowel rest
  • Aggressive antibiotic therapy

Outcome and Prognosis

The prognosis depends on the etiology of the fistula. For benign processes, the prognosis is generally good provided sepsis is absent or limited and the entity is recognized quickly.

Malignancy that is sufficiently advanced to cause a renoalimentary fistula carries a poor prognosis. This is not due to the fistula itself, but because of the tumor.

Future and Controversies

Renoalimentary fistula will likely remain an occasional sequela of percutaneous nephrostomy tube placement, but management is relatively straightforward. With percutaneous radiofrequency ablation and cryoablation becoming a more popular and viable treatment option, patients should be aware that renoalimentary fistula is a potential complication of them. The use of hydrodissection during radiofrequency ablation with normal saline and vigilance of surrounding structures during these procedures should help keep the development of fistulae to a minimum.

In many cases, renoalimentary fistulae are secondary to neglected treatment of chronic disease. Continued efforts at early diagnosis and treatment of underlying problems should decrease the incidence of renoalimentary fistulae and improve the prognosis.