Introduction Inappropriate antidiuretic hormone secretion syndrome can be a serious adverse event of cisplatin‐based chemotherapy. Cisplatin had to be changed to other drugs or chemotherapy completely discontinued in earlier reported cases. Case presentation Three cycles of bleomycin, etoposide, and cisplatin chemotherapy were planned for a 40‐year‐old man with a diagnosis of lymph node recurrence of testicular cancer. On day 9, he suffered from vomiting and mental disturbance. Severe hyponatremia (110 mEq/L) with low plasma osmolality led to a diagnosis of a syndrome of inappropriate antidiuretic hormone secretion, and infusions of hypertonic saline and salt intake were prescribed. Second and third courses of bleomycin, etoposide, and cisplatin chemotherapy could then be given with careful electrolyte management. Conclusion Continuation of cisplatin administration with precise electrolyte adjustment can be a treatment option in regimens where cisplatin is essential for achieving optimal antitumor efficacy.

Idiopathic onset of portal vein thrombosis (PVT) and/or superior mesenteric vein thrombosis (SMVT) in young adults could be associated with congenital thrombophilia, resulting from mutations in the genes encoding antithrombin, protein C, or protein S. This report describes a 39-year-old man who developed symptoms of cholangitis and was incidentally found to have PVT and SMVT with cavernous transformation. The patient was found to have protein C deficiency (activity: 42-53%, antigen: 46%). Gene sequencing revealed a heterozygous mutation at exon 8 c.793C>T (p. Leu265Phe). The history of this patient suggested that thrombosis in his splanchnic venous system developed due to alcoholism plus congenital protein C deficiency. The patient has been managed with complete abstinence from alcohol and treatment with oral rivaroxaban.