TUBULOINTERSTITIAL NEPHRITIS AND ACUTE RENAL FAILURE: A CASE OF PRIMARY RENAL LYMPHOMA.

We present an anusual case of acute renal failure and nephritis tubulointerstitial caused by infiltration by undifferentiated diffuse B-cell lymphoma.

We report a 61-year-old female patient with non-intentioned weight loss (6 kilograms), fatigue and sporadic lumbar pain one month previously admission. She was medical evaluated with a diagnosis of urinary tract infection receiving antibiotic treatment with partial improvement. One week previously admission, she presented nausea, sporadic vomiting, and persistence of symptoms reason for which she went to the hospital.

On admission, patient didn´t had any important pathological history. The evaluation revealed stable vital signs and physical examination was normal. Laboratory studies showed hemoglobin 12.2 mg/dL, creatinine in 5.83 mg/dL, urea in 80.4 mg/dL, total protein in 7.78 mg/dL and albumin in 4.39 mg/dL. Urinalysis presented leukocyturia and albuminuria 1+. Other results are described in Table 1.

She underwent a nephrology consultant at emergency room, where was diagnosed of acute renal failure and probable tubulointerstitial nephritis with indication of hospitalization and start of hemodialysis.

During hospitalization, 24-hours protein collection result was 350 mg, kidney ultrasonography evaluation was normal, immunological studies (complement, ANA titers, ENA profile, ANCA titers) were negative, infections (HIV, B Hepatitis, C Hepatitis, TORCH profile, syphilis) were excluded and urine culture was negative. Under negative results, we decided to perform a renal biopsy (Figure 1).

Renal biopsies show cortex and medullar zones, in where we found round cells of intermediate size, moderate anisocytosis in which they were immersed occasional renal tubules and sporadic glomerulus (02 in total) with mild fibrosis capsular. Immunohistochemical studies were done and CD20 stain were positive (3+). Results showed undifferentiated diffuse B-cell lymphoma.

After the biopsy result, a contrast-tomography exam was done to evaluate nodular compromise, but no affectation of nodules was described. The kidneys were enlarged and with regular shape as shown in figure 2, no masses were described. Finally, the patient was diagnosed with primary renal lymphoma bilateral and was referred to the oncology unit to initiate R-CHOP scheme.

Tubulointerstitial nephritis is an important cause of acute kidney failure and chronic kidney disease. This entity is characterized by an infiltration of inflammatory cells in the renal interstitial area. Renal biopsy remains as the gold standard to diagnose this entity in where probable cause can be guided with the type of inflammatory cells involved. There are many causes of tubulointerstitial nephritis described such as secondary to infections, drug-induced, autoimmune disorders, obstructive uropathy, heavy metal-induced, hereditary disorders, neoplasm and idiopathic. 

Neoplastic causes are the rarest etiology of tubulointerstitial nephritis, and within these, lymphomas are even not common. Generally, neoplasms infiltrate renal parenchyma from tumor cells surrounding it and its affectation is secondary. There are few cases reported of primary source, specifically primary renal lymphomas, with no more than 70 cases reported in the literature and the majority are of non-Hodgkin lymphoma. Its development is not elucidated yet, because the kidney does not have naturally lymphocytes inside it. The proposed pathogenesis implicated in its origin is the lymphatic renal parenchyma, or it can be because of any chronic inflammatory process that cause cellular changes in lymphocytes and predispose to neoplasms.

The most common initial clinical presentation can be since asymptomatic presentation or with weight loss, fever, and flank pain. Laboratory studies report hematuria, leukocyturia and sub-nephrotic proteinuria range.

Computed tomography is the most sensitive image for evaluation ok kidneys in patients with suspected renal lymphoma. The forms of presentation detected by computed tomography are multiple masses, solitary masses, contiguous retroperitoneal or perirenal extension and infiltrative disease. Infiltrative presentation encompasses 20% of the forms of presentation, affects bilaterally with enlargement of the kidney. Contrast images are needed to demonstrate poorly defined interface with the normal renal parenchyma, a characteristic of focal areas of infiltrative disease.

The prognosis reported is poor, and the median survival is less than a year. The management include chemotherapy with scheme R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone) and in some cases, nephrectomy is recommended. Results of this management are only described in case report or case series.

In our case patient, she is receiving chemotherapy and intermitent hemodyalisis, and also continuosly evaluated by nephrology and oncology team.