Nephropleural Fistula
A nephropleural fistula — also called a reno-pleural or pyelopleural fistula — is an abnormal communication between the renal collecting system and the pleural space, producing a urinothorax. The most common cause is iatrogenic injury during supracostal percutaneous nephrolithotomy (PCNL); spontaneous fistulae arise from longstanding obstructive uropathy with forniceal rupture, and a third mechanism is penetrating thoracoabdominal trauma.[1][2] The diagnosis is anchored by the single biochemical fact that pleural-fluid creatinine exceeds serum creatinine — a finding pathognomonic for urinothorax.[1][3]
See also: The Kidneys, Fistulas landing page.
Etiology
The pleural reflection extends inferiorly along the posterior thoracic wall and crosses the 11th and 12th ribs, placing the upper-pole collecting system in close apposition to the pleural cavity. Any process that decompresses urine across this boundary can establish a fistula.
| Mechanism | Typical setting |
|---|---|
| Iatrogenic — supracostal PCNL | Above-11th-rib puncture is the dominant mechanism; pleural injury rates of 15–34% have been reported with above-11th access vs. ~1% for subcostal access[4][5][6] |
| Iatrogenic — other | Percutaneous nephrostomy, antegrade ureteroscopy, renal biopsy, ablation procedures[2] |
| Obstructive uropathy with forniceal rupture | UPJ obstruction, distal ureteral stone, pelvic malignancy compressing the ureter — urine decompresses retroperitoneally and tracks across the diaphragm into the pleural space (the classic spontaneous urinothorax)[1][7] |
| Penetrating or blunt thoracoabdominal trauma | Direct collecting-system injury with concurrent diaphragmatic disruption[2] |
| Renal / perirenal abscess | Erosion through Gerota's fascia and the diaphragm; xanthogranulomatous pyelonephritis is a recognized substrate[2] |
| Malignancy | Rare; renal cell carcinoma or urothelial carcinoma with diaphragmatic extension[2] |
Pathogenesis
The right kidney is partially sheltered by the liver, while the left upper pole sits closer to the pleural reflection — a small predominance of left-sided fistulae has been described in PCNL series.[5] When the pleural-renal communication is established, negative intrathoracic pressure during inspiration continuously aspirates urine across the defect, producing rapidly accumulating pleural effusion. If urine is sterile and the cavity is decompressed, the fistula will frequently close once the urinary tract is diverted; if urine is infected, the cavity becomes a urinary empyema with trapped lung.[2][5]
Clinical Presentation
Presentation is dictated by tempo and infection status:
- Acute post-PCNL — chest pain, dyspnea, falling oxygen saturation, or unexpectedly large output from a chest tube placed for routine pleural injury; output may be straw-colored urine rather than serous fluid.[5]
- Subacute / spontaneous — progressive pleuritic chest pain, dyspnea, and a large unilateral pleural effusion ipsilateral to obstructive uropathy or flank pain.[1][7]
- Infected — fever, leukocytosis, frank empyema, sepsis. Trapped lung and parapneumonic-pattern fluid in a patient with recent renal instrumentation should raise the diagnosis.
Hematuria, flank pain, decreased urine output, and a known stone or obstructive history are often present; the pleural effusion is typically massive and ipsilateral to the renal pathology.[1][7]
Evaluation
The diagnosis hinges on pleural-fluid biochemistry combined with imaging confirmation of the urinary source.
Thoracentesis and pleural-fluid analysis
| Finding | Interpretation |
|---|---|
| Pleural-fluid creatinine / serum creatinine ratio > 1.0 | Diagnostic of urinothorax — the only effusion in which pleural creatinine exceeds serum creatinine[1][3][8] |
| Low pH, low glucose | Common; urinothorax classically behaves as an exudate by Light's criteria but can be transudative[1][3] |
| Urine-like odor and color | Supportive but neither sensitive nor specific |
| Positive culture | Implies urinary empyema; mandates source control |
Imaging
| Modality | Role |
|---|---|
| Chest radiograph | Initial detection of effusion; post-PCNL rib-level review for puncture height[5][9] |
| CT chest, abdomen, and pelvis with delayed urographic phase | Workhorse: demonstrates pleural fluid, the renal source (stone, obstruction, perinephric collection), and often the tract itself[2] |
| Antegrade or retrograde pyelography | Direct demonstration of contrast extravasation into the pleural space — most sensitive study when other imaging is equivocal[5] |
| Nephrostogram | Useful for follow-up confirmation of fistula closure before tube removal[5] |
| Pleural drainage with creatinine assay of effluent | Confirms diagnosis when effusion reaccumulates after thoracentesis |
Management
The cornerstone is proximal urinary diversion plus pleural drainage, with definitive treatment of the underlying obstruction or stone.[2][5]
Step 1 — control the pleural cavity
- Tube thoracostomy for symptomatic effusion, suspected empyema, or massive accumulation
- Repeated therapeutic thoracentesis for small, non-infected, slowly-accumulating effusions in selected patients
- VATS decortication for trapped lung or established empyema with pleural rind
Step 2 — divert the urinary tract
- Ureteral stent is the simplest first-line diversion when retrograde access is feasible[5]
- Percutaneous nephrostomy when retrograde access fails, when the upper tract is grossly dilated, or when a working access tract already exists from prior PCNL[2][5]
- Combined stent + nephrostomy for complex or proximal injuries
Step 3 — treat the underlying cause
- Complete clearance of any obstructing stone burden
- Pyeloplasty or endopyelotomy for UPJ obstruction
- Drainage and antibiotics for perirenal abscess
- Oncologic management for malignant erosion
Refractory or non-salvageable kidney
- Operative repair of the collecting-system defect — open or laparoscopic / robotic — is reserved for cases that fail prolonged diversion
- Partial or simple nephrectomy for a non-functional or destroyed pole / kidney with persistent fistula
- Diaphragmatic repair at the same setting if a discrete defect is identified
Most iatrogenic post-PCNL nephropleural fistulae resolve with the diversion-plus-drainage strategy alone; operative reconstruction is uncommon.[5]
Prevention
The most effective intervention is avoidance of supracostal access when subcostal access is feasible.[4][5] When supracostal access is required, end-expiratory puncture, minimizing tract dilation, intraoperative chest fluoroscopy, and a low threshold for routine post-PCNL chest imaging reduce the rate of unrecognized pleural injury.[5][9]
Outcomes
With early recognition, prompt pleural drainage, and adequate urinary diversion, most nephropleural fistulae heal within days to a few weeks, with chest tube and stent / nephrostomy removed in sequence after a confirmatory nephrostogram.[5] Delayed recognition with established empyema, persistent obstruction, or a nonfunctional kidney drives the small subset that requires operative repair or nephrectomy.
References
1. García-Pachón E, Padilla-Navas I. "Urinothorax: Case Report and Review of the Literature With Emphasis on Biochemical Diagnosis." Respiration. 2004;71(5):533–536. doi:10.1159/000080642
2. Toubes ME, Lama A, Ferreiro L, et al. "Urinothorax: A Systematic Review." J Thorac Dis. 2017;9(5):1209–1218. doi:10.21037/jtd.2017.04.22
3. Stark DD, Shanes JG, Baron RL, Koch DD. "Biochemical Features of Urinothorax." Arch Intern Med. 1982;142(8):1509–1511. doi:10.1001/archinte.1982.00340210101019
4. Munver R, Delvecchio FC, Newman GE, Preminger GM. "Critical Analysis of Supracostal Access for Percutaneous Renal Surgery." J Urol. 2001;166(4):1242–1246. doi:10.1016/s0022-5347(05)65750-9
5. Lallas CD, Delvecchio FC, Evans BR, Silverstein AD, Preminger GM, Auge BK. "Management of Nephropleural Fistula After Supracostal Percutaneous Nephrolithotomy." Urology. 2004;64(2):241–245. doi:10.1016/j.urology.2004.04.009
6. Hopper KD, Yakes WF. "The Posterior Intercostal Approach for Percutaneous Renal Procedures: Risk of Puncturing the Lung, Spleen, and Liver as Determined by CT." AJR Am J Roentgenol. 1990;154(1):115–117. doi:10.2214/ajr.154.1.2104692
7. Salcedo JR. "Urinothorax: Report of 4 Cases and Review of the Literature." J Urol. 1986;135(4):805–808. doi:10.1016/s0022-5347(17)45855-7
8. Salyer WR, Eggleston JC, Erozan YS. "Urinothorax: An Unusual Cause of Pleural Effusion." JAMA. 1971;218(11):1683–1684. doi:10.1001/jama.1971.03190240037008
9. Ogan K, Corwin TS, Smith T, et al. "Sensitivity of Chest Fluoroscopy Compared With Chest CT and Chest Radiography for Diagnosing Hydropneumothorax in Association With Percutaneous Nephrostolithotomy." Urology. 2003;62(6):988–992. doi:10.1016/s0090-4295(03)00792-1