A 49-year-old man was diagnosed as having gastric carcinoma (PT2N1M0, Stage IV) in September 2021. Subtotal gastrectomy was performed in September 2021, then tegafur-gimeracil-oteracil potassium capsules were administered for six courses. Nivolumab 300 mg was given on 28 March 2022 and 18 April 2022. He did not have a medical history of hypertension, diabetes, or kidney disease.
Symptoms with hematuria, pollakiuria, painful micturition, and fever developed on the second day after the second course of nivolumab therapy. Physical examination: T (Temperature) 38 C, P(Pulse) 100 bpm (beats per minute), R (Respiration) 18 bpm (breaths per minute), BP (Blood pressure) 100/65 mmHg. The abdomen was soft, no tenderness and rebound. His bilateral renal percussive pain was positive. There was no edema in the lower limbs.
Urinalysis showed RBCs of 13,298/microl, WBCs of 2,506/microl, and proteinuria 3+. Urinary NGAL is 54.6 micro/l. Blood tests showed WBCs of 9,300/microl (neutrophils 72.8%, eosinophils 1.3%), C-reactive protein of 35.5 mg/L, lactate dehydrogenase of 164 U/L, sCr of 102 mumol/l, and ESR of 21 mm/h. Antibiotics were given. However, his sCr level significantly elevated to 190 micromol/l (baseline sCr 50.9 mumol/l). The autoimmune antibody profile, immunoglobulin profile, and complement level were within normal range. Fungal D-glucan test and limulus test were negative. Serum procalcitonin was 0.13 ng/ml. Serum T-spot and urinary Mycobacterium tuberculosis were negative. Blood culture was negative. Repeated urine cultures were negative. Urinary ultrasonography and CT showed mild hydronephrosis, dilated ureters, and thickened bladder wall ( Figures 2F, G ). Antibiotics were given, and urinary symptoms were not relieved. The patient was eventually diagnosed as having immune-related ureteritis and cystitis at the third week of urinary symptoms. Methylprednisolone was administered at 60 mg (body weight 44.5 kg, equivalent to 1.7 mg/kg/day of prednisone) intravenously, and body temperature returned to normal quickly and urinary irritation was relieved after 3 days of therapy. After 4 weeks of methylprednisolone, sCr returned to the baseline level and urinary WBC/RBC turned negative. The patient, who wished to initiate antitumor therapy earlier, complicated by intestinal fungal infections and steroid-induced diabetes during steroid treatment, reduced the dose of methylprednisolone quickly and discontinued it on 25 August 2022 by himself:assertion. Then, the patient had a recurrence of urinary irritation symptoms, gross hematuria, and sterile pyuria on 29 August. The methylprednisolone tablets were restarted at 16 mg, and the urinary irritation symptoms were alleviated quickly and urinary WBC/RBC returned to negative. The current dose of methylprednisolone tablets is 10 mg. Urinary WBC/RBC was negative from 26 September 2022 until now. His sCr was 60 mumol/l on 17 October 2022. The timeline of the treatment course was summarized in  Figure 5 .