Approach to the Critical Patient

Immediate Priorities

Hemodynamic and neurologic threats from severe hypernatremia

Stabilization Targets

Sodium correction rate — non-negotiable safety limit

Escalation and Consults

Escalation triggers requiring ICU or step-down admission

History

Core Symptoms

Polyuria characteristics

Polydipsia characteristics

Onset and Timing

Onset pattern as diagnostic clue

Triggers and Exposures

Precipitating events

Alarm Features

High-risk features requiring urgent evaluation

Medical and Family History

Past medical history relevant to DI

Family history

Review of Systems

System-specific symptoms contextualizing DI etiology

Physical Exam

Vital Signs and Hemodynamic Assessment

Vital sign patterns in DI

Hydration Status

Dehydration findings

Neurologic Examination

Mental status and CNS findings

Endocrine and Physical Findings

Features suggesting pituitary or hypothalamic pathology

Pitfalls

Physical exam pitfalls in DI

Differential Diagnosis

Life-Threatening Causes of Polyuria

Central DI (AVP deficiency) — ICD-10: E23.2

Nephrogenic DI (AVP resistance) — ICD-10: N25.1

Polyuria Mimics

Primary polydipsia (psychogenic polydipsia) — ICD-10: F50.89

Diabetes mellitus — osmotic diuresis from glucosuria — ICD-10: E11.65

Osmotic diuresis from other solutes

Chronic kidney disease — ICD-10: N18.9

Hypercalcemia-induced nephrogenic DI — ICD-10: E83.52

Hypokalemia-induced nephrogenic DI — ICD-10: E87.6

Gestational DI — ICD-10: O26.89

Beer potomania / tea-and-toast diet

Laboratory Tests

Essential Initial Labs

Serum sodium and osmolality — diagnostic cornerstone

Urine osmolality and specific gravity

Serum glucose

Serum calcium and potassium

BUN and creatinine

Serum electrolytes panel — sodium, potassium, chloride, bicarbonate

Advanced Diagnostic Labs

Plasma copeptin — AVP surrogate marker

Anterior pituitary function panel when panhypopituitarism suspected

Lithium level if on lithium therapy

Monitoring Labs

Ongoing monitoring on treatment

Diagnostic Tests

Scoring Systems

Novel AVP-D diagnostic score (Lancet Diabetes Endocrinol 2025)

Water deprivation test — classic approach being supplanted by copeptin

MRI

MRI pituitary and hypothalamus — first-line imaging for all new central DI

CT

CT head — role is limited but important in acute settings

Ultrasound

Ultrasound has limited direct role in DI diagnosis

Disposition

Admission Indications

Inpatient admission criteria

ICU Admission Criteria

ICU-level care indications

Discharge Criteria

Safe discharge criteria

Specialist Consultation

Consultation pathways

Treatment

Acute Severe Hypernatremia

IV free water replacement — cornerstone of acute management

Desmopressin — Central DI Treatment

Desmopressin (DDAVP) — first-line treatment for central DI

Nephrogenic DI Treatment

Remove offending agent — first and essential step

Thiazide diuretics — paradoxical antidiuretic effect

NSAIDs — adjunct for severe nephrogenic DI

Low-sodium low-protein diet as adjunct

Electrolyte Correction

Address reversible causes of nephrogenic DI

Intercurrent Illness Management

DI management during acute illness

Special Populations

Pregnancy

Gestational DI — unique mechanism and management

Geriatric

Older adults — increased vulnerability and modified management

Pediatrics

Congenital and pediatric DI — distinct presentation and management

Background

Epidemiology

Prevalence and incidence data

Mortality and morbidity

Pathophysiology

AVP deficiency (central DI) mechanism

AVP resistance (nephrogenic DI) mechanism

Compensatory polydipsia

Triphasic response after pituitary surgery

Therapeutic Considerations

Treatment selection by DI subtype

Patient Discharge Instructions

copy discharge instructions

What is Diabetes Insipidus?

Your medications

Hydration and diet

Warning signs — Return to the emergency room immediately if you experience

Follow-up instructions

Sick day rules

References

Guidelines and Key Sources

Tomkins M, Lawless S, Martin-Grace J, Sherlock M, Thompson CJ

Flynn K, Hatfield J, Brown K, Vietor N, Hoang T

Newell-Price J, Drummond JB, Gurnell M, et al

Atila C, Refardt J, Christ-Crain M

Fenske W, Refardt J, Chifu I, et al

Refardt J, Atila C, Chifu I, et al

Winzeler B, Cesana-Nigro N, Refardt J, et al

Atila C, Chifu I, Drummond JB, et al

Christ-Crain M, Winzeler B, Refardt J

Adams NC, Farrell TP, O'Shea A, et al

Brooks EK, Inder WJ

Vaz de Castro PAS, Bitencourt L, et al

Guarino S, Diplomatico M, Marotta R, et al

Korkmaz HA, Kapoor RR, Kalitsi J, et al

Joshi RS, Pereira MP, Osorio RC, et al

Garrahy A, Thompson CJ

Miller NE, Rushlow D, Stacey SK