Case Report of a Unique but Likely Not Uncommon Etiology of a Markedly Elevated Serum Carbohydrate Antigen 19-9 (CA 19-9)

Abstract

Tumor markers are an extremely valuable clinical tool in the diagnosis, staging, response to treatment, and monitoring of patients with GI and other malignancies. Clinicians should be aware of the sensitivity and specificity profile when utilizing tumor markers in clinical practice to avoid false positives and false negatives. We report a 45 year-old male referred for moderate LUQ abdominal pain, weight loss, and a markedly elevated carbohydrate antigen 19-9 (CA 19-9) of 983 U/ml. CA 19-9 is frequently elevated in patients with pancreatic cancer and cholangiocarcinoma, but also other GI malignancies such as colorectal, esophageal, and hepatocellular carcinoma. CA19-9 has a sensitivity of 78% with a specificity of 83% in symptomatic patients, with false positives often secondary to pancreatitis and cirrhosis. The patient's initial workup included a normal CBC, BMP, LFTs and both amylase and lipase. The patient underwent a CT scan with pancreatic protocol, magnetic resonance cholangiopancreatography (MRCP), endoscopic ultrasound of pancreas (EUS), EGD, and colonoscopy that showed a normal appearing pancreas and hepatobiliary anatomy. The CT scan revealed left renal atrophy with hydronephrosis, a rare cause of elevated CA19-9 in the urologic literature. Due to persistent concern about the etiology of the patient's symptoms, we suggested a left nephrectomy with follow up CA19-9 after surgery in addition to immunostaining of the resected tissue. Interestingly, the ureter revealed marked localization of CA19-9 with normalization of CA19-9 serum levels and resolution of the patient's of abdominal pain. We report a unique but likely not uncommon cause of a markedly elevated CA19-9 in a patient with hydronephrosis that resolved after nephrectomy.