Tubulointerstitial nephritis New
Tubulointerstitial nephritis (TIN) is a heterogeneous group of kidney diseases characterized by inflammation and injury of the renal tubules and interstitium, with relative sparing of the glomeruli.
It represents an important cause of acute kidney injury (AKI) and may progress to chronic kidney disease (CKD) if untreated.
Classification of TIN
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Characteristics of TIN
- Proteinuria (usually mild to moderate, tubular type)
- Non-glomerular hematuria
- Leukocyturia (especially in infectious or inflammatory forms)
- Dysuria (mainly in infectious etiologies)
Tubular dysfunction may also lead to:
- impaired urine concentrating ability
- electrolyte disturbances (e.g., acidosis, potassium imbalance)
Acute TIN
Acute forms are characterized by rapid onset of renal dysfunction associated with inflammatory infiltration of the interstitium. includes:
- Acute bacterial TIN
- Acute hypersensitivity (drug-induced) TIN
- Parainfectious TIN
- Idiopathic forms
Acute bacterial TIN
Most commonly arises from ascending urinary tract infection. Predisposing factors:
- Congenital anomalies (e.g., duplex kidney, vesicoureteral reflux)
- Urinary obstruction (lithiasis, strictures, prostatic enlargement)
Clinical presentation
- Fever and systemic inflammatory signs
- Flank or lumbar pain
- Dysuria and urinary frequency
- Possible oliguria
Examination
Physical findings:
- shortness of breath, sweating, febrile illness, often accompanied by chills
- active occupation of the relief position
- positive tapottement
Urinalysis:
- leukocyturia (constant)
- bacteriuria should also always be present. If the detection of bacteria fails, the possibility of TB infection must be considered
- non-glomerular erythrocyturia
- proteinuria usually <2 g/day
Laboratory tests:
- leukocytosis
- elevated inflammatory markers
Microbiology:
- urine culture mandatory (commonly E. coli, Klebsiella)
Imaging:
- ultrasound may show inflammatory changes
Renal biopsy is generally not required in typical cases.
Therapy
- Empirical antibiotics → adjusted according to culture
- Common regimens include cephalosporins, aminoglycosides, fluoroquinolones
- Treatment duration: usually ≥2 weeks
Acute hypersensitivity TIN
This form is typically drug-induced (e.g., antibiotics, NSAIDs).
Pathogenesis
Immune-mediated reaction with interstitial infiltration by lymphocytes and eosinophils.
Clinical features
- Fever
- Skin rash
- Arthralgia
- Renal dysfunction
Latency of 1–6 weeks after drug exposure is typical.
Examination
Urine findings
- non-glomerular hematuria
- eosinophiluria
- variable proteinuria
Blood tests
- eosinophilia (suggestive but not universal)
Biopsy
- interstitial inflammation ± granulomas
Therapy
- Immediate withdrawal of the causative drug
- Corticosteroids if renal function does not improve
Chronic TIN
Chronic forms are characterized by progressive interstitial fibrosis and tubular atrophy, leading to irreversible renal damage. Main types:
- Chronic bacterial TIN
- Reflux nephropathy
- Analgesic nephropathy
- Toxic/metabolic nephropathies
Chronic bacterial TIN
Usually develops after recurrent acute infections.
Clinical features
- often asymptomatic between episodes
- gradual decline in renal function
Findings
- persistent leukocyturia
- bacteriuria
- mild proteinuria
Therapy
- treatment of acute exacerbations
- long-term prevention in recurrent cases
Reflux nephropathy
Associated with vesicoureteral reflux (VUR) leading to repeated renal injury.
Pathogenesis
Retrograde urine flow → recurrent infections → scarring.
Clinical features
- recurrent UTIs (especially in childhood)
- enuresis in children
- later: hypertension, renal insufficiency
Diagnosis
- urine abnormalities (leukocyturia, bacteriuria)
- imaging (voiding cystography, scintigraphy)
Therapy
- management of infections
- surgical correction of reflux
- treatment of CKD complications
Analgesic nephropathy
Results from chronic abuse of analgesics (historically phenacetin-containing drugs).
Features
- slowly progressive renal insufficiency
- hematuria
- renal colic (papillary necrosis)
- hypertension
Complications
- increased risk of urothelial carcinoma
- other manifestations (psychosomatic, bone, cardiovascular, hematological and gastrointestinal disorders).
