What is Pyelitis?
Pyelitis is an inflammation of the renal pelvis, which is distinct from pyelonephritis that involves inflammation of both the renal pelvis and kidney parenchyma. 1 While the term "pyelitis" is less commonly used in modern medical literature, it represents a specific condition affecting the collecting system of the kidney.
Clinical Definition and Characteristics
Pyelitis specifically refers to inflammation limited to the renal pelvis (the funnel-like structure that collects urine from the kidney's collecting ducts). This differs from pyelonephritis, which involves inflammation of both the renal pelvis and the kidney parenchyma 1.
The clinical presentation of pyelitis may include:
- Flank pain
- Fever (though typically less severe than in pyelonephritis)
- Urinary symptoms (frequency, urgency)
- Pyuria and bacteriuria
Types of Pyelitis
Several specific forms of pyelitis have been identified:
Encrusted pyelitis: A rare but serious condition characterized by calcified encrustations in the wall of the upper urinary tract with surrounding inflammation 2, 3. Key features include:
- Often caused by urea-splitting organisms (particularly Corynebacterium group D2)
- Predisposing factors: previous urological procedures, immunosuppression, prolonged antibiotic use
- Can lead to destruction of kidney tissue and end-stage renal failure if not properly treated
- Diagnosis requires CT imaging, crystalluria analysis, and specialized bacterial cultures
- Treatment involves antibiotics (often glycopeptides like vancomycin), urine acidification, and sometimes surgical removal of encrustations 4, 5
Infectious pyelitis: Caused by bacterial infection of the renal pelvis without significant involvement of the renal parenchyma.
Relationship to Other Urinary Tract Infections
Pyelitis exists on a spectrum of urinary tract infections:
- Cystitis: inflammation limited to the bladder
- Pyelitis: inflammation of the renal pelvis
- Pyelonephritis: inflammation of both renal pelvis and kidney parenchyma
Pyelonephritis typically presents with more severe systemic symptoms than pyelitis, including high fever, chills, malaise, vomiting, and flank pain/tenderness 1.
Diagnosis
Diagnosis of pyelitis requires:
- Clinical symptoms
- Evidence of inflammation (pyuria)
- Presence of pathogenic bacteria in urine
- Imaging studies to confirm involvement of the renal pelvis without significant parenchymal involvement
Treatment Approach
Treatment of pyelitis generally follows similar principles to treating upper urinary tract infections:
- Appropriate antibiotic therapy based on culture and sensitivity testing
- For uncomplicated cases, oral antibiotics may be sufficient
- For complicated cases or those with risk factors, initial parenteral therapy may be warranted
- In cases of encrusted pyelitis, specialized treatment with antibiotics, urine acidification, and sometimes surgical intervention is required 2, 3
Clinical Importance
Early recognition and appropriate treatment of pyelitis is important to prevent:
- Progression to pyelonephritis
- Development of renal scarring
- Potential for chronic kidney disease in severe or recurrent cases
- Complications such as sepsis in high-risk populations
While pyelitis as a distinct entity receives less attention in current medical literature than pyelonephritis, recognizing the specific involvement of the renal pelvis can help guide appropriate diagnostic and therapeutic approaches.