Tuberculosis and tubulointerstitial nephritis: an intriguing puzzle

Challenges in the Diagnosis and Management of Nephrotic Syndrome in a Child With Multisystemic Tuberculosis

We report the case of a child who had tuberculosis associated with nephrotic syndrome. In this case, it was difficult to identify if the renal involvement was due to renal infection with mycobacterium tuberculosis, the consequence of nephrotoxicity of anti-bacillary drugs, or due to new onset of nephrosis. Management was complex as the use of high-dose steroids can disseminate the infection.

Serologic and urinary characteristics of laboratory-confirmed genitourinary tuberculosis at a tertiary hospital in the Philippines

Background

Genitourinary tuberculosis (GUTB) is known to cause high rates of structural organ damage, however, literature on its biochemical manifestations is limited. Additionally, local studies in the Philippine setting, where cases are rampant, are few and dated. This study aimed to determine the serologic and urinary profile of patients with GUTB admitted at a tertiary hospital within January 2009 to March 2020 and their association with short-term outcomes.

Methods

This retrospective study included 112 patients with laboratory-confirmed GUTB (i.e., positivity in acid-fast smear, polymerase chain reaction, culture, or histology). Demographic data, clinical characteristics, laboratory and radiologic findings, histopathology reports, treatment, and short-term outcomes were recorded.

Results

Bladder (54.5%) and kidney (36.4%) were the most affected organs. The male:female ratio was 1:1.15, and the mean age was 35.79 ± 18.29 years. Weakness (14.29%) was the most common chief complaint. A majority presented with anemia (83.04%), while several had leukocytosis (41.96%) and thrombocytosis (26.79%). Hypoalbuminemia (58.10%), impairment of renal function (36.94%), and electrolyte abnormalities such as hyponatremia (50.93%), hypercalcemia (20.19%), and hypokalemia (21.82%) were common. Proteinuria (67.96%) and pyuria (67.96%) were the most frequent abnormal findings, followed by hematuria (51.46%), acidic urine (45.63%) and low specific gravity (31.07%). Age, leukocytosis, and the need for pressors were all significantly associated with mortality (p values of <0.001, 0.010, and <0.001, respectively).

Conclusions

The young age at presentation with severe clinical and laboratory manifestations may reflect local epidemiology as TB continues to be widespread in the country. Apart from the more commonly cited abnormalities in literature, multiple electrolyte imbalances and urinary concentration defects were also observed in many cases, possibly indicating tubulointerstitial involvement—a complication increasingly mentioned in case reports. As several patient characteristics were found to be associated with the high mortality rates observed in the study, further research is recommended to explore predictive modeling.

Idiopathic granulomatous interstitial nephritis and isolated renal sarcoidosis: Two diagnoses of exclusion

Granulomatous interstitial nephritis is a rare finding in renal biopsy caused by drugs, infections, and inflammatory or autoimmune diseases. Idiopathic cases account for 18% of granulomatous interstitial nephritis in native kidneys. Sarcoidosis and drugs are the most common causes of granulomatous interstitial nephritis in Western countries, while in India tuberculosis prevails. Few cases of renal sarcoidosis without extrarenal involvement, that is, isolated renal sarcoidosis, have been reported. The diagnostic criteria of isolated renal sarcoidosis remain, however, unclear. Extrarenal sarcoidosis and other etiologies of granulomatous interstitial nephritis, in particular drug-related, have to be excluded. Some of these patients may develop extrarenal manifestations during follow-up. Changes in calcium and vitamin D metabolism are frequently observed in renal sarcoidosis and support its diagnosis. While non-necrotizing granulomas are a feature of sarcoidosis and drug-induced granulomatous interstitial nephritis, they also prevail in tuberculosis-associated granulomatous interstitial nephritis. Granulomatous interstitial nephritis caused by sarcoidosis and drugs usually responds to steroid therapy. A poor response to steroids may indicate an infectious etiology such as tuberculosis and should lead to a review of the initial diagnosis. This article gives an overview of the various etiologies of granulomatous interstitial nephritis, their frequency and histopathological characteristics, as well as potential biomarkers associated with renal sarcoidosis.

Acute tubulointerstitial nephritis in a patient with early bronchial tuberculosis

Patients with chronic kidney disease (CKD) are commonly at high risk of tuberculosis (TB). Conversely, TB rarely causes tubulointerstitial nephritis. A 75-year-old Japanese man who was undergoing periodic follow-ups for CKD stage G3aA3 with membranous nephropathy was diagnosed with acute kidney injury (AKI) (estimated glomerular filtration rate [eGFR]: 15 mL/min/1.73 m²) without prerenal AKI. He reported developing recent-onset cough 3 weeks prior to presenting to us. Renal biopsy revealed acute tubulointerstitial nephritis along with known membranous nephropathy. CD4⁺ helper T cells comprised most lymphocytes in the tubulointerstitium. Results of the interferon-gamma release assay, sputum smear test, polymerase chain reaction (PCR), and culture test were positive for TB. Chest computed tomography revealed thickening of the left bronchial wall; therefore, a diagnosis of early bronchial TB was made; his urine culture and PCR were negative for TB. At four months after TB treatment with no immunosuppressive therapy, his eGFR improved to 50 mL/min/1.73 m², and based on this progress, the AKI was diagnosed as tuberculosis-associated tubulointerstitial nephritis (TATIN). Although TATIN typically occurs with chronic or miliary tuberculosis, it is very rare in early bronchial TB. Identification of TATIN is important in kidney diseases of unknown etiology, and treatment with anti-TB drugs is necessary.

[Renal granulomatous nephritis: Histopathological point of view]

Granulomatous interstitial nephritis (NIG) is a rare form of interstitial nephritis that can be related to acute or chronic clinical presentation. NIG is characterized by granulomas located to the renal interstitium and composed of either epithelioid histiocytes with giant cells and/or of foreign body reaction. The symptoms are unspecific and associate varying degrees of renal failure with abnormal urinanalysis. Extra-renal signs may point to systemic disease. Pathological examination from kidney percutaneous biopsy or surgical resection is required to assert NIG diagnosis and to guide the etiological research. The main causes of NIG are sarcoidosis, drug reactions, mycobacterial infections and crystalline nephropathies. Sarcoidosis is characterized by non-necrotic and well-formed giant cell epithelioid interstitial granulomas. Drug reactions have less well-defined granulomas with inconstant eosinophils. The presence of caseous necrosis within giant cell and epithelioid granulomas leads to infectious NIG diagnosis (tuberculosis and fungal infection). Identification of crystals within foreign body reaction can be improved by polarized light study. Xanthogranulomatous pyelonephritis and malakoplakia are rarer causes of NIG characterized by patches of histiocytes associated with inconstant giant cells. Differential diagnoses of NIG are represented by granulomatous reactions centered on glomeruli and vessels (vasculitis and emboli of cholesterol crystals). Less than 10% of NIG are idiopathic. The prognosis and the treatment vary according to the cause. The factors of poor renal prognosis are chronic irreversible tubulo-interstitial injury (tubular atrophy and interstitial fibrosis).

Severe tubulointerstitial nephritis: tracking tuberculosis even in the absence of renal granuloma

Extra-pulmonary tuberculosis is frequently located in the kidneys and, in such cases, could be associated with a granulomatous interstitial nephritis. Granulomas are not always detected, especially in human immunodeficiency virus (HIV)-positive patients. We report here a case of tubulointerstitial nephritis without granulomas in an HIV-negative patient. Since all laboratory tests failed to isolate Mycobacterium tuberculosis in the kidney, a targeted biopsy guided by positron emission tomography-computed tomography was performed on a mediastinal node, revealing a positive culture. After 6 months of treatment, no recovery of the renal injury has been observed.

Single-centre experience of granulomatous interstitial nephritis-time for a new approach?

Background: Differentiating between renal-limited sarcoidosis and tuberculosis (TB) infection as a cause of granulomatous interstitial nephritis (GIN) can be difficult. This series compares clinical features and response to treatment between the different underlying aetiologies in order to propose a management algorithm for GIN to assist with diagnosis and treatment.

Methods: This retrospective study reports on all patients presenting with a histological diagnosis of GIN between 2000 and 2012 at our unit.

Results: Twenty-one patients were identified, 57% were male and the mean age was 53 years. Eight cases were associated with sarcoidosis with evidence of extra-renal disease and five with renal-limited sarcoidosis. Five patients had GIN that may have been related to TB infection or to renal-limited sarcoidosis, and three were idiopathic or drug related. All those with sarcoidosis were treated with steroids and renal function, as measured by estimated glomerular filtration rate (eGFR), improved from a mean of 24 mL/min at baseline to 37 mL/min at 1 year. Baseline eGFR was 19 mL/min in those with possible TB infection. Four received steroids as well as anti-TB drugs. Anti-TB therapy was delayed in four patients by a mean of 22 months due to difficulties in diagnosis. Two patients with TB developed end-stage kidney disease and the remaining three patients had a mean eGFR of 28 mL/min at 1 year.

Conclusions: This series represents the largest cohort of patients with GIN in the UK and supports previous findings that patients with sarcoid have a favourable outcome with steroid treatment. Those with TB have an inferior prognosis, perhaps due to delayed diagnosis. We suggest an algorithm when investigating a diagnosis of GIN with the aim of expediting diagnosis and considering a trial of anti-TB therapy in order to prevent deterioration of renal function.

Long-term outcome in biopsy-proven acute interstitial nephritis treated with steroids

Background: There are no prospective randomized controlled trials describing the outcome of acute interstitial nephritis (AIN) treated with steroids, and retrospective studies are limited.

Methods: We identified adult patients with a diagnosis of AIN without glomerular pathology over a 14-year period. Treated patients all received oral prednisolone and three also recieved IV methylprednisolone. Data were collected retrospectively on estimated glomerular filtration rate (eGFR), change in eGFR from time of biopsy, dependence on renal replacement therapy (RRT) and mortality, and outcomes were analysed according to the treatment prescribed.

Results: A total of 187 eligible patients with AIN were identified and 158 were treated with steroids. There was no difference in median eGFR or dependence on RRT at the time of biopsy. Steroid-treated patients had significantly higher eGFR at all time points post-biopsy up to 24 months, when median eGFR was 43 mL/min in the steroid-treated group and 24 mL/min in the untreated group (P  =  0.01). Fewer patients in the steroid-treated group were dialysis dependent by 6 months (3.2% versus 20.6%, P  =  0.0022) and 24 months (5.1% versus 24.1%, P  =  0.0019).

Conclusions: This large retrospective study suggests a benefit of steroids in treatment of AIN with greater improvement in eGFR and fewer patients progressing to end-stage renal disease.

Changes in the aetiology, clinical presentation and management of acute interstitial nephritis, an increasingly common cause of acute kidney injury

Acute interstitial nephritis (AIN) is an important cause of acute kidney injury that has experienced significant epidemiological and clinical changes in the last years. The classical presentation, mostly induced by antibiotics and accompanied by evident hypersensitivity manifestations (skin rash, eosinophilia, fever) has been largely replaced by oligosymptomatic presentations that require a higher index of suspicion and are increasingly recognized in the elderly, having non-steroidal anti-inflammatory agents and proton pump inhibitors as frequent offending drugs. Drug-induced AIN continues to be the commonest type, but it requires a careful differential diagnosis with other entities (tubulointerstitial nephritis with uveitis syndrome, IgG4-related disease, drug reaction with eosinophilia and systemic symptom syndrome, sarcoidosis and other systemic diseases) that can also induce AIN. Cortico-dependant, relapsing AIN is a recently recognized entity that poses an important therapeutic challenge. Although corticosteroids are widely used in drug-induced AIN to speed kidney function recovery and avoid chronic kidney disease, their efficacy has not been tested by randomized controlled trials. New diagnostic tests and biomarkers, as well as prospective therapeutic studies are needed to improve AIN diagnosis and management.