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Renal tuberculosis (renal TB) is a chronic granulomatous infection of the kidney caused by Mycobacterium tuberculosis, usually arising from hematogenous spread of pulmonary TB.

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It is the most common form of genitourinary tuberculosis, which is the second most frequent extrapulmonary site after lymph nodes.

Etiopathogenesis

• Primary route: Hematogenous seeding of bacilli into renal cortex from pulmonary or other systemic TB.
• Initial cortical granulomas remain dormant for years.
• Reactivation → granulomatous destruction → papillary necrosis → caseation and cavitation.
• Spread into:
  • Collecting system → strictures, calyceal deformity.
  • Ureter → ureteric strictures.
  • Bladder → contracted, thick-walled bladder ("thimble bladder").
• Late stage: autonephrectomy (non-functioning calcified kidney).

![Features of active urinary tract tuberculosis. Infection begins in the renal cortex, where it may be latent. When activated, bacteria enter the medulla via loop of Henle or lymphatics more so than hematogenously and may form granulomas (papillitis stage), which can coalesce to form abscesses (ulcerocavernous stage). Some of these abscesses erode into the pelvicalyceal system, which results in urothelial thickening (pyelitis and ureteritis stage). The draining bacilli colonize the bladder wall, beginning at the vesicoureteric junction, resulting in irregular wall thickening (cystitis)

Das, C.J., Razik, A., Tchoquessi, R.L.N. et al. Multimodality imaging of urinary tract tuberculosis. Abdom Radiol 50, 770–783 (2025). https://doi.org/10.1007/s00261-024-04526-y](attachment:5bd74b69-44ad-437e-b376-a1c33d00d2dd:image.png)

Features of active urinary tract tuberculosis. Infection begins in the renal cortex, where it may be latent. When activated, bacteria enter the medulla via loop of Henle or lymphatics more so than hematogenously and may form granulomas (papillitis stage), which can coalesce to form abscesses (ulcerocavernous stage). Some of these abscesses erode into the pelvicalyceal system, which results in urothelial thickening (pyelitis and ureteritis stage). The draining bacilli colonize the bladder wall, beginning at the vesicoureteric junction, resulting in irregular wall thickening (cystitis)

Das, C.J., Razik, A., Tchoquessi, R.L.N. et al. Multimodality imaging of urinary tract tuberculosis. Abdom Radiol 50, 770–783 (2025). https://doi.org/10.1007/s00261-024-04526-y

![Features of chronic urinary tract tuberculosis, and their sequelae. Calcification of parenchymal granulomas and caseous material in the calyces result in amorphous/punctate and lobar-pattern calcification, respectively. The latter may fill the structure but more commonly is found at the periphery. Parenchymal fibrosis results in cortical scarring. Infundibular stenosis causes uneven caliectasis, a distinctive feature of tuberculosis. A relatively contracted renal pelvis with a Kerr’s kink and multifocal ureteric strictures results from scarring within the urinary tract. Chronic cystitis can result in a low-capacity urinary bladder with a thickened wall, referred to as a thimble bladder. The prior two process can result in vesicoureteral junction stenosis and reflux

Das, C.J., Razik, A., Tchoquessi, R.L.N. et al. Multimodality imaging of urinary tract tuberculosis. Abdom Radiol 50, 770–783 (2025). https://doi.org/10.1007/s00261-024-04526-y](attachment:ab40eec6-d556-4955-86f0-9e436e1bc416:image.png)

Features of chronic urinary tract tuberculosis, and their sequelae. Calcification of parenchymal granulomas and caseous material in the calyces result in amorphous/punctate and lobar-pattern calcification, respectively. The latter may fill the structure but more commonly is found at the periphery. Parenchymal fibrosis results in cortical scarring. Infundibular stenosis causes uneven caliectasis, a distinctive feature of tuberculosis. A relatively contracted renal pelvis with a Kerr’s kink and multifocal ureteric strictures results from scarring within the urinary tract. Chronic cystitis can result in a low-capacity urinary bladder with a thickened wall, referred to as a thimble bladder. The prior two process can result in vesicoureteral junction stenosis and reflux

Das, C.J., Razik, A., Tchoquessi, R.L.N. et al. Multimodality imaging of urinary tract tuberculosis. Abdom Radiol 50, 770–783 (2025). https://doi.org/10.1007/s00261-024-04526-y

Clinical Features

• Often insidious, appears years after primary TB.
• Flank pain, dysuria, hematuria.
• Recurrent sterile pyuria (urine WBCs with negative culture on routine media).
• Frequency, urgency (if bladder involved).
• Systemic: fever, weight loss, night sweats (often absent).

Radiology

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IVU classic triad: calyceal deformity, infundibular strictures, parenchymal cavities.

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