American Journal of Medicine, internal medicine, medicine, health, healthy lifestyles, cancer, heart disease, drugs

An Overlooked Cause of Polyuria

Computed tomography of the neck.

A 40-year-old woman presented to the Outpatient Department with complaints of frequent urination and excessive thirst for 3 months. She was passing large volumes of urine throughout the day and night, but she denied dysuria, urgency, or hesitancy. She used to consume 2 cups of tea in a day. Twenty-four-hour urine output was 6 L, with corresponding increase in fluid intake. There was no relevant medical history, except for the frequent use of proton pump inhibitors and laxatives for pain epigastrium and constipation, respectively. She reported no weight loss, headache, visual changes, use of diuretics, or alteration in behavior. Clinical examination was unremarkable. Blood glucose profile, renal function test, and urine examination were normal. The patient was referred to our institute for water deprivation test. However, in view of gastrointestinal symptoms like pain epigastrium and constipation, hypercalcemia was suspected and the patient was evaluated accordingly. Biochemical profile revealed high-serum calcium (3.1 mmol/L) with low-serum phosphate (0.67 mmol/L). Serum parathyroid hormone levels were markedly elevated (412 ng/L), with normal 25 (OH) vitamin D levels (78 nmol/L). Computed tomography of the neck showing 3 × 2 cm heterogeneously enhancing soft tissue lesion within the left retrotracheal space, merging with the lower pole of the left lobe of the thyroid (Figure). Technetium (Tc-99m)-labeled sestamibi scan revealed the presence of hot focus in the left inferior pole of the thyroid in the delayed image, consistent with parathyroid adenoma. The patient received fluid replacement with saline and bisphosphonates. After therapy, serum calcium levels decreased, and osmotic symptoms subsided. The patient underwent surgical removal of the adenoma, and histopathology confirmed the diagnosis.

Polyuria in adults is defined as urine output more than 3 L/d (>40 mL/kg/d).1 A thorough clinical history and quantification of 24-hour urine volume is essential to distinguish between polyuria and increased urinary frequency. Once polyuria is confirmed, drug history is essential to rule out a potential pharmacological cause, particularly use of diuretics, lithium, alcohol, and caffeine. Blood glucose profile helps us to rule out diabetes mellitus. Other rare causes include diabetes insipidus and psychogenic polydipsia, which are confirmed with the help of water deprivation test.

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-Mandeep Singla, MDDM, Abhinav Gupta, MD

This article originally appeared in the February issue of The American Journal of Medicine.

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