Abstract
Emphysematous pyelonephritis is a rare, life-threatening necrotizing infection that is typically characterized by classic urinary symptoms. However, it is exceptionally rare for emphysematous pyelonephritis to manifest with predominant gastrointestinal symptoms, a deceptive mimicry that often masks the underlying renal pathology and leads to significant diagnostic delays. We report the case of a woman in her 60s with type 2 diabetes whose initial presentation was limited to vomiting and diarrhea, suggesting acute gastroenteritis. In the absence of typical urological distress, her condition rapidly worsened, and she developed septic shock and altered mental status within 48 h. Computed tomography confirmed Huang–Tseng class 3B emphysematous pyelonephritis with extensive destruction of the right renal parenchyma. Recognizing the irreversible tissue necrosis and failure of medical therapy, a decisive transition to emergency nephrectomy was performed. This timely surgical intervention successfully arrested the fulminant progression, leading to hemodynamic stabilization and recovery. This case underscores that emphysematous pyelonephritis rarely masquerades as gastroenteritis; in diabetic patients, such atypical manifestations followed by rapid clinical deterioration necessitate immediate computed tomography evaluation. Furthermore, when imaging reveals extensive gas formation and clinical stability is lost, prompt and resolute surgical source control is a critical, life-saving measure for ensuring patient survival.
Keywords
Introduction
Emphysematous pyelonephritis (EPN) is a rare, life-threatening necrotizing infection characterized by renal gas formation.1–3 Despite advances in antimicrobial therapy and intensive care, EPN remains a fatal emergency requiring early diagnosis and timely source control.3–5 Computed tomography (CT) is indispensable for confirming the diagnosis and assessing disease extent, utilizing classifications such as the Huang–Tseng system to guide the escalation from medical therapy to surgical intervention.2,4,5 However, this diagnostic workflow is frequently disrupted when EPN presents with misleading gastrointestinal features rather than classic urinary symptoms.4,6,7 We report a case of EPN in a diabetic patient in whom such “gastroenteritis mimicry” masked the underlying pathology, leading to a significant diagnostic delay. Consequently, the disease exhibited fulminant progression with extensive necrosis, ultimately necessitating emergency nephrectomy as a life-saving measure. This case highlights the critical need for early CT screening and decisive surgical intervention when conservative windows are missed.2,6,7
Case presentation
The patient was a woman in her 60s with a 5-year history of type 2 diabetes mellitus. She used insulin routinely; however, she did not monitor her blood glucose regularly. Three days prior to her transfer to our hospital, she developed sudden vomiting (brown vomitus) and diarrhea. The following day, she presented to another hospital for symptomatic treatment. However, during her 2-day stay at that facility, her condition deteriorated with the onset of fever (maximum body temperature: 38.4°C) and altered mental status (agitation and delirium). Notably, clear lower urinary tract symptoms were absent throughout this course. She was diagnosed with septic shock and acute kidney injury at that hospital. Laboratory tests revealed marked inflammation (white blood cell count, 25.58 × 109/L and procalcitonin level, >240 ng/mL) and renal impairment (serum creatinine level, 219 μmol/L and unknown premorbid renal function). Abdominal CT confirmed EPN, revealing a small amount of gas in the right kidney, ureter, and perirenal space (Figure 1(a)). Due to the severity of her condition, she was urgently transferred to Peking University Shenzhen Hospital in Shenzhen, China, in February 2025.
Serial abdominal CT scans and histopathological analysis demonstrating the rapid progression of emphysematous pyelonephritis (EPN). (a) Initial CT scan obtained on the second day of illness showing gas within the right renal parenchyma and ureter, accompanied with perirenal free gas (red circle), consistent with EPN. (b) Preoperative CT scan obtained 1 h preoperatively on the fourth day of illness demonstrating extensive destruction of the right renal parenchyma with multiple coalescing gas foci (red circle), indicating rapid disease progression. (c–e) Postoperative pathological findings: H&E staining reveals renal parenchymal necrosis (red circle, c), focal abscess (yellow circle, c), necrotic renal tubules (green circle, d), and necrotic glomeruli (blue circle, d); Gram staining identifies Gram-positive bacilli (black circle, e). (f) Follow-up CT scan performed 2 days after emergency right nephrectomy showing the empty renal fossa (red circle) with minimal localized exudation at the surgical site. CT: computed tomography; H&E: Hematoxylin and Eosin.
On admission, the patient was comatose and critically ill, with a body temperature, 38.0°C; pulse rate, 115 beats/min; respiratory rate, 25 breaths/min; and blood pressure, 96/63 mmHg (maintained with norepinephrine). She required mechanical ventilation and hemodialysis. Physical examination revealed right costovertebral angle tenderness. Laboratory investigations indicated severe sepsis (white blood cell count, 26.79 × 109/L and procalcitonin level, 202.8 ng/mL) and acute kidney injury (serum creatinine level, 146 μmol/L; Table 1). Urinalysis showed leukocyte esterase 2+, with 15–20 white blood cells and 5–10 red blood cells per high-power field; however, midstream urine culture yielded no bacterial growth. Contrast-enhanced CT confirmed Huang–Tseng class 3B EPN with extensive destruction of the right renal parenchyma and gas accumulation in the collecting system, ureter, and perirenal/retroperitoneal spaces (Figure 1(b)). Based on imaging and clinical severity, a diagnosis of EPN complicated by septic shock and multiple organ dysfunction was established.
Comparison of perioperative laboratory parameters.
POD: postoperative day; HPF: high-power field.
↑ indicates values above the reference range; ↓ indicates values below the reference range.
After admission to the intensive care unit (ICU), aggressive resuscitation was initiated, including fluid management, vasoactive support, and empirical broad-spectrum antibiotics (1 g intravenous imipenem every 6 h and 0.5 g vancomycin every 12 h). Blood cultures yielded methicillin-resistant Staphylococcus epidermidis in one of three samples. Although the clinical significance of this single isolate was interpreted with caution, intravenous vancomycin was continued for 3 days to ensure coverage, while imipenem was administered for 7 days. Despite maximal medical therapy, the patient remained in persistent septic shock with rapid clinical deterioration. Based on multidisciplinary evaluation, we concluded that the right kidney was unsalvageable, and definitive source control was urgently required.
Emergency laparoscopic right nephrectomy was performed. Intraoperatively, the perirenal fascia was under high tension with severe inflammatory adhesions. Upon capsular entry, a large gas-containing cavity filled with necrotic debris was revealed. The kidney and surrounding necrotic tissues were completely excised. Postoperative pathology confirmed severe necrotizing infection (Figure 1(c) and (d)), and Gram staining of the tissue revealed Gram-positive bacilli (Figure 1(e)). Following surgery, the patient’s condition stabilized in the surgical ICU. The antimicrobial regimen was later de-escalated to latamoxef (1 g twice daily for 7 days). Follow-up CT showed a clean surgical bed (Figure 1(f)), and laboratory markers showed significant improvement (Table 1). She was discharged after full recovery.
The reporting of this study conforms to the Case Report (CARE) guidelines. 8 The timeline of diagnosis, assessments, treatments, and outcomes is illustrated in Figure 2. Written informed consent for publication was obtained from the patient’s legal representative before preparing the case report. All patient details have been deidentified.
Timeline of the clinical course illustrating rapid deterioration and subsequent recovery. The timeline summarizes key clinical events and management milestones from symptom onset to discharge, including the pre-hospital period (Day 1), initial presentation at another hospital (Days 2–3), and subsequent admission to Peking University Shenzhen Hospital (Days 4–14). Gastrointestinal symptoms (vomiting and diarrhea) appeared on Day 1, followed by fever and delirium during Days 2–3, which led to an initial diagnosis of emphysematous pyelonephritis (EPN). On Day 4, the patient’s condition progressed to septic shock and multiple organ failure; CT imaging confirmed Huang–Tseng class 3B EPN, prompting an emergency right nephrectomy. Following surgery, clinical stabilization was achieved by Day 7, and the patient was successfully discharged on Day 14. CT: computed tomography.
Discussion
EPN is a catastrophic, necrotizing infection of the renal parenchyma characterized by gas production within the kidneys and perirenal tissues.1,2,4, It predominantly affects patients with uncontrolled diabetes mellitus, who account for >90% of all reported cases.1,4 The pathogenesis involves high tissue glucose levels which provide a favorable substrate for gas-forming organisms, primarily Escherichia coli and Klebsiella pneumoniae, for fermentation and gas generation (predominantly carbon dioxide, followed by hydrogen and ammonia).2,4 Although the overall mortality rate has decreased to approximately 13%–25% with advances in modern management, EPN remains a life-threatening condition, particularly in patients with septic shock or extensive tissue necrosis who have a significantly higher mortality risk.1,3,6 Although the classic triad of fever, flank pain, and pyuria is well-recognized, atypical clinical presentations can mask the underlying pathology, creating a period of increased susceptibility to diagnostic errors.2,4,7
Against this background, the educational value of this case is reflected in four critical aspects. First, the deceptive clinical presentation poses a significant diagnostic pitfall.2,4,6 The patient presented predominantly with gastrointestinal symptoms (vomiting and diarrhea) followed by rapid neurological deterioration (delirium/coma), notably in the absence of classic urinary symptoms. Such “clinical mimicry” can easily lead to misdiagnosis as acute gastroenteritis, metabolic encephalopathy, or primary central nervous system events, resulting in catastrophic treatment delays.4,6,9 Therefore, in diabetic patients presenting with sepsis of unclear origin, particularly when accompanied with altered mental status and markedly elevated inflammatory markers, clinicians must maintain a high index of suspicion for severe urinary tract infection.2,6,7 Although standard diagnostic tools such as urinalysis and microscopy remain the primary methods for diagnosing urinary tract infections, early abdominal CT is specifically recommended to exclude EPN when high-risk features are present, even in the absence of localizing urinary signs.2,4
Second, the radiological extent of gas distribution serves as a vital prognostic biomarker.2,4,5 In this case, the extensive gas phenotype characterized by the involvement of the renal parenchyma, collecting system, ureter, and bladder, along with extension into the perirenal and pararenal spaces, indicated a fulminant infectious burden and extensive tissue necrosis.4,10 When such imaging findings are compounded by hemodynamic instability or progressive organ dysfunction, a single static scan may underestimate the velocity of disease progression.2,5,6 Consequently, low-threshold dynamic re-imaging and continuous multidisciplinary reassessment are warranted to guide timely and appropriate intervention.
Third, the atypical microbiological findings in this case warrant consideration. Although EPN is predominantly associated with Gram-negative bacteria, tissue Gram staining here revealed Gram-positive bacilli.2,4,11 Given the prior administration of broad-spectrum antibiotics and negative urine cultures, this finding likely reflects the morphology of residual bacteria modified by antimicrobial therapy rather than identifying the primary live causative pathogen; however, the possibility of a mixed infection cannot be completely ruled out.10,11
Fourth, definitive source control is the cornerstone of survival in patients with severe EPN.2,6 Current medical management of EPN emphasizes a stratified approach, including early recognition, rapid sepsis resuscitation, use of broad-spectrum antibiotics, and strict glycemic control.4,7,12 Although current algorithms advocate the use of renal-sparing strategies involving antibiotics combined with percutaneous drainage in localized and stable disease, such conservative measures are associated with high failure rates in fulminant cases.2,11 For patients with Huang–Tseng class 3B or 4 EPN or high-risk features such as septic shock, altered consciousness, acute kidney injury, and coagulopathy, delayed radical intervention is associated with marked increase in the mortality rate.2,6 In this patient, the decision to proceed with emergency nephrectomy was vindicated by the intraoperative findings of a large necrotic gas cavity, confirming that organ preservation was not feasible. The rapid postoperative recovery of circulatory and organ functions further supports the strategy of early and decisive nephrectomy for high-risk and salvage-refractory EPN.2,6,7
The limitations of this report include its single-case design and the fact that prior antibiotic therapy may have obscured the complete microbiological profile.
Conclusion
EPN is a fatal infection with a very narrow therapeutic window. In diabetic patients with severe infection of unclear origin or altered consciousness, CT should be performed early to confirm diagnosis and assess the disease extent. When high-risk features such as extensive gas, extrarenal spread, and shock are present and the affected kidney is considered unsalvageable, definitive source control should be instituted promptly. This case suggests that for patients with high-risk fulminant EPN in whom conservative management fails to achieve effective source control, timely nephrectomy can play a decisive role in survival and prognosis.
Footnotes
Acknowledgment
Not applicable.
Author contributions
W.C. and G.W. collected the clinical data and wrote the manuscript. S.Y., J.D., and M.L. prepared the figures and performed the literature review. L.B. and X.F. supervised the study and critically revised the manuscript. All authors read and approved the final manuscript.
Availability of data and materials
All clinical data generated or analyzed during this study are included in this published article.
Clinical trial number
Not applicable.
Consent for publication
Written informed consent was obtained from the patient’s legal representative before preparing the case report.
Declaration of conflicting interests
The authors declare no competing interests.
Ethics approval and consent to participate
Not applicable.
Funding
This work was supported by the Shenzhen Clinical Research Center for Urology and Nephrology (LCYSSQ20220823091403008).
