Renal tuberculosis

Posted By Wael Nemattalla
Renal tuberculosis

65 years old male with suspected bilateral renal stones. Splenic and hepatic calcifications are seen due to old granulomas. Left renal parenchymal scarring is seen. Noted also left PUJ obstruction.

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  • Wael Nemattalla 2013-12-11 08:01:22

    Renal tuberculosis





    Renal tuberculosis, a subset of genitourinary tuberculosis, accounts for 15-20% of extra-pulmonarytuberculosis and can result in varied and striking radiographic appearances.

    Tuberculosis can involve both the renal parenchyma and the collecting system (calyces, renal pelvis, ureter, bladder and urethra) and results in different clinical presentations and radiographic appearances. This article focuses on the renal parenchyma, calyces and renal pelvis. For discussion of lower urinary tract and genital involvement please refer to the article on genitourinary tuberculosis.





    Clinical presentation

    Clinical features are often non specific and include :

    • haematuria

    • flank pain

    • constitutional symptoms

    Diagnosis can be obtained by culturing multiple first-morning-void urine samples, or by histology of imaging guided biopsy or surgical specimens, although as with tuberculosis infection elsewhere the diagnosis is not always easy to confirm 4.





    Pathology

    Renal infection results from haematogenous spread at the time of primary infection, with multiple micro-abscesses developing at the site of periglomerular capillary seeding. Normal host immunity is usually able to dampen the disease with the usual development of a small inactive granuloma.

    Usually there is a long latency between primary infection and presentation which in most case occurs due to host immunity becoming compromised. These quiescent granulomas then can reactivate, grow and eventually communicate with the calyces, leading to downstream infection.





    Radiographic features

    Both the renal parenchyma and the upper collecting system (calyces and renal pelvis) can be involved. The former is usually seen associated with the latter, which is the most commonly involved site in the genitourinary tract.

    Infection limited to the renal parenchyma has two morphological appearances 4:

    1. pyelonephritis

    o appearances are similar to pyelonephritis caused by other organisms

    o hypoperfusion and swelling of all or part of the kidney

    2. pseudotumoural type

    o single or multiple nodules

    o mimics renal cell carcinoma

    Usually the collecting system is involved (either in isolation or in combination with the parenchyma), and appearances vary according to the stage of disease 4.

    • early

    o papillary necrosis (single or multiple) resulting in uneven caliectasis

    • progressive

    o multifocal strictures and hydronephrosis

    o mural thickening and enhancement (on cross-sectional imaging)

    • endstage

    o progressive hydronephrosis and parenchymal thinning

    o dystrophic calcification



    Plain film

    Plain film findings focus on calcification, which is seen in 25-45%, at various stages of disease.

    • triangular in papillary necrosis

    • focal or amorphous : putty kidney (endstage)



    Fluoroscopy - IVP

    Traditional plain film IVP is quite sensitive to renal tuberculosis with only 10% of affected patients having normal imaging. Features include:

    • parenchymal scars 50%

    • moth eaten calyces : early finding

    • irregular caliectasis

    • phantom calyx

    • hydronephrosis

    Lower urinary tract signs (see bladder and ureteric tuberculosis) also recognised include:

    • Kerr kink 3

    • sawtooth ureter

    • pipe-stem ureter

    • beaded or corkscrew ureter

    • thimble bladder



    Ultrasound

    Sonographic appearances are non-specific and variable, depending on the stage of disease.

    • early

    o normal kidney or small focal cortical lesions with poorly defined border

    o + / - calcification.

    • progressive

    o papillary destruction with echogenic masses near calyces.

    o distorted renal parenchyma.

    o irregular hypoechoic masses connecting to collecting system; no renal pelvic dilatation.

    o mucosal thickening + / - ureteric and bladder involvement.

    o small, fibrotic thick-walled bladder.

    o echogenic foci or calcification (granulomas) in bladder wall near ureteric orifice.

    o localised or generalised pyonephrosis.

    • endstage

    o small, shrunken kidney, "paper-thin" cortex and dense dystrophic calcification in collecting system.

    o may resemble chronic renal disease.

    Ultrasound is less sensitive than CT in detection of :

    • calyceal, pelvic or ureteral abnormalities.

    • isoechoic parenchymal masses.

    • small calcifications.

    • small cavities that communicate with collecting system.





    CT

    CT is the most sensitive modality for visualising renal calcifications and CT IVP is more sensitive at identifying all manifestations of renal tuberculosis 4.

    • early

    o papillary necrosis (single or multiple) resulting in uneven caliectasis

    • progressive

    o multifocal strictures can affect any part of the collecting system

    o generalised or focal hydronephrosis

    o mural thickening and enhancement

    o poorly enhancing renal parenchyma, either due to direct involvement or due to hydronephrosis

    • endstage

    o progressive hydronephrosis results in very thin parenchyma, mimicking multiple thin walled cysts

    o amorphous dystrophic calcification eventually involves the entire kidney (known asputty kidney)





    Treatment and prognosis

    Multi-drug treatment is essential, however despite treatment, stricturing can progress.

    The role of nephrectomy is controversial and depends on the degree of renal impairment, bilateral vs unilateral disease and the status of the lower urinary tract.

    Nephrectomy, partial nephrectomy or cavernostomy can be performed both open and endoscopically5.



    Differential diagnosis

    General imaging differential considerations include

    • papillary necrosis

    • medullary sponge kidney

    • TCC (transitional cell carcinoma) of renal tract

    • SCC (squamous cell carcinoma) of renal tract

    • xanthogranulomatous pyelonephritis (XGP)





    Source:

    http://radiopaedia.org/articles/renal_tuberculosis

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