Nephrogenic diabetes insipidus

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Arginine vasopressin binds the V2 receptor on collecting-duct principal cells, increasing apical aquaporin-2 water channels and permitting concentration of urine. AVPR2 dysfunction, AQP2 dysfunction or acquired disruption of this pathway prevents the kidney responding appropriately. Large volumes of dilute urine produce thirst, nocturia and sleep disruption. Sodium concentration reflects the balance between water loss and replacement, so a normal sodium in a freely drinking patient does not exclude substantial nephrogenic disease.

Lithium is the leading acquired medicine cause. It enters principal cells partly through epithelial sodium channels and can reduce aquaporin expression and cause chronic structural injury. The clinical response to polyuria must balance renal harm with the psychiatric benefit of lithium; patients should not stop it themselves. Hypercalcaemia and sustained hypokalaemia reduce concentrating ability, while obstruction and chronic interstitial disease can create partial resistance. Congenital AVPR2 disease is usually X-linked and often severe in boys; AQP2 disease may be recessive or dominant and affects either sex.

Diagnosis proceeds from volume and tonicity, not from thirst alone. A timed urine collection confirms output; simultaneous blood and urine samples help separate water from solute diuresis. Supervised water deprivation with a desmopressin phase may distinguish central deficiency, nephrogenic resistance and primary polydipsia, but severe baseline hypernatraemia or clear hypotonic polyuria may make deprivation unsafe or unnecessary. Copeptin-based protocols exist in specialist centres and local expertise determines the test.

Key points

Nephrogenic diabetes insipidus is renal resistance to arginine vasopressin, now also termed AVP resistance, causing hypotonic polyuria despite an intact thirst and hormone response.
Confirm true polyuria by measured volume rather than urinary frequency; in adults a 24-hour output above about 3 litres is a useful threshold but size and intake matter.
Exclude osmotic diuresis from glucose, urea, mannitol or diuretics and primary polydipsia before undertaking specialised water-balance testing.
Acquired causes include lithium, hypercalcaemia, hypokalaemia, obstruction and tubulointerstitial disease; congenital disease most often involves X-linked AVPR2 or AQP2 variants.
People with intact thirst and unrestricted water can maintain sodium, but illness, fasting, impaired cognition, dependence or restricted access can reveal life-threatening dehydration quickly.
Paired plasma sodium or osmolality and urine osmolality show whether urine is inappropriately dilute; water-deprivation testing must be supervised by an experienced endocrine or renal service.
Desmopressin usually has little effect in complete nephrogenic disease, unlike central AVP deficiency, although partial responses and mixed states require specialist interpretation.
Treat the cause, guarantee water access, reduce dietary solute with dietetic advice and consider thiazide or amiloride under specialists; chronic NSAID therapy is not routine because renal and gastrointestinal harms can outweigh benefit.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Acquired collecting-duct resistance

Lithium, hypercalcaemia, sustained hypokalaemia, urinary obstruction and chronic tubulointerstitial disease can reduce collecting-duct responsiveness to arginine vasopressin.

Inherited AVP-signalling defects

Pathogenic AVPR2 variants, commonly X-linked, or AQP2 variants impair receptor signalling or collecting-duct water-channel function and may present in infancy.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Preserved vasopressin release
Rising plasma tonicity appropriately stimulates thirst and arginine vasopressin secretion, distinguishing the core defect from absent central hormone production.
2
Collecting-duct resistance
V2-receptor signalling or aquaporin-2 availability is reduced, so principal cells cannot increase water permeability adequately in response to circulating hormone.
3
Hypotonic polyuria
Water remains within the tubular lumen and large volumes of dilute urine are excreted despite an intact physiological drive to conserve water.
4
Uncompensated water loss
Thirst and drinking may preserve sodium until illness, fasting, dependency or impaired cognition interrupts access, when hypernatraemia and hypovolaemia develop quickly.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Water diuresis

Persistent large-volume pale urine, thirst and nocturia with low urine osmolality point to impaired water conservation rather than simple urinary frequency.

Hypernatraemic dehydrationRed flag

Dry mucosae, hypotension, tachycardia, lethargy, irritability, confusion or seizure after reduced water access signals dangerous uncompensated loss.

Lithium association

Polyuria and polydipsia during long-term lithium therapy may be nephrogenic DI, but hyperglycaemia, hypercalcaemia, CKD and lithium toxicity still need assessment.

Congenital presentationRed flag

An infant with relentless thirst, fever, vomiting, constipation, poor growth and recurrent hypernatraemia may have inherited AVPR2 or AQP2 disease.

Partial resistance

Moderately dilute urine and some desmopressin response can occur, so binary interpretation without baseline osmolality and supervised protocol is unreliable.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Measured 24-hour urineFirst step
Why
Confirm polyuria and quantify ongoing water loss.
Interpretation and limitations
A volume above roughly 3 litres daily supports adult polyuria, but interpret against body size, intake, renal function and collection completeness.
02
Paired plasma and urine osmolality
Why
Determine whether urine concentration is appropriate for the circulating water state.
Interpretation and limitations
High or high-normal plasma tonicity with inappropriately dilute urine indicates impaired antidiuresis; very high urine osmolality suggests solute diuresis instead.
03
Serum sodium, glucose, calcium and potassium
Why
Grade urgency and identify osmotic or reversible metabolic causes.
Interpretation and limitations
Hypernatraemia signals inadequate water replacement; hyperglycaemia causes solute diuresis, while hypercalcaemia and hypokalaemia can produce AVP resistance.
04
Supervised dynamic testing
Why
Differentiate AVP deficiency, AVP resistance and primary polydipsia when baseline studies remain ambiguous.
Interpretation and limitations
Specialists interpret urine response to controlled dehydration and desmopressin, or use a validated copeptin protocol; never perform an informal fluid-withholding test.
05
Lithium and renal assessment
Why
Evaluate drug exposure, toxicity and chronic kidney effects where lithium is relevant.
Interpretation and limitations
Obtain a correctly timed level, eGFR, urea and electrolytes, calcium, thyroid tests and medicine interactions; toxicity can occur despite a level that appears unremarkable.
06
Genomic testing
Why
Confirm inherited disease and guide family counselling in early-onset or familial cases.
Interpretation and limitations
AVPR2 and AQP2 results require renal-genetic interpretation, carrier counselling and correlation with phenotype; an uncertain variant is not independently diagnostic.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Primary polydipsia

Excess water intake suppresses vasopressin and dilutes urine; supervised dynamic testing and baseline plasma tonicity distinguish this from renal hormone resistance.

Central AVP deficiency

Insufficient hormone secretion causes similarly dilute polyuria but usually shows a stronger concentrating response to desmopressin during specialist testing.

Osmotic diuresis

Glucose, urea, mannitol or diuretics increase solute excretion and usually produce a less dilute urine than a pure water diuresis.

Urinary frequency without polyuria

Cystitis, overactive bladder and outlet obstruction cause frequent small voids; a measured daily volume separates these from true excess water excretion.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01VerifyProve hypotonic polyuriaFirst stepA patient reports frequent urination and excessive thirst.

1Distinguish urinary frequency from high volume using a bladder history, fluid chart or complete 24-hour urine measurement.
2Pair urine osmolality with plasma sodium or osmolality and screen glucose, calcium, potassium, renal function and diuretic or SGLT2 use.
3If hypotonic polyuria persists, refer for supervised endocrine or renal testing rather than advising home water restriction.

02RescueManage hypernatraemic water lossWater access fails and sodium rises with neurological or circulatory features.

1Assess airway, circulation, weight, sodium trend and urine losses; restore intravascular volume with the appropriate isotonic fluid first when shock is present.
2Calculate a provisional free-water plan but adjust it frequently to serial sodium, urine output and ongoing losses, using local critical-care limits for correction.
3Maintain continuous access to water or prescribed enteral or intravenous replacement and treat the precipitant with renal, endocrine or paediatric advice.

03ReverseAddress an acquired causeLithium, calcium, potassium, obstruction or interstitial injury is implicated.

1Correct hypercalcaemia or hypokalaemia and assess obstruction and kidney disease while reviewing every medicine that affects water balance.
2For lithium, contact the mental-health prescriber and renal or endocrine team to weigh dose reduction, substitution or cessation against relapse risk.
3Reassess urine volume and osmolality after intervention because concentrating defects may improve slowly or persist despite stopping the exposure.

04ReduceLower chronic urine volumeSubstantial polyuria persists despite reliable water access and cause treatment.

1Use renal-dietetic advice to moderate sodium and unnecessary protein load without causing malnutrition, thereby reducing obligatory solute excretion.
2Consider a thiazide-type diuretic and, for lithium-associated disease, amiloride through specialist prescribing with close sodium, potassium and renal monitoring.
3Reserve NSAID or partial-desmopressin strategies for exceptional specialist-led situations after explicit assessment of renal, gastrointestinal, cardiovascular and hyponatraemia risks.

Key medicines and prescribing safety4 treatments · regimens, roles and cautions

Produces a paradoxical antidiuretic effect through mild volume contraction, greater proximal reabsorption and reduced delivery to the collecting duct.

Thiazide-type diuretic

Select a locally available agent and low starting dose only under renal or endocrine advice, then titrate against measured urine volume, blood pressure and electrolytes.

May cause hyponatraemia, hypokalaemia, gout, hypotension and AKI. In a lithium user it can raise lithium concentration markedly, requiring prescriber-led adjustment and frequent levels.

Blocks epithelial sodium channels and may reduce lithium entry into collecting-duct cells while helping reduce polyuria.

Amiloride

Use specialist-selected dosing from the current formulary, particularly in lithium-associated disease, with early and repeated potassium, creatinine and lithium checks.

Can cause dangerous hyperkalaemia, especially with CKD, ACE inhibitors, ARBs or potassium supplements; fixed-dose combinations and renal thresholds require review.

Replaces AVP activity and is highly effective in central deficiency, but renal resistance usually limits benefit in nephrogenic disease.

Desmopressin

Do not use routinely for complete nephrogenic DI; any trial for a documented partial response belongs to a specialist protocol with strict fluid and sodium advice.

Excess fluid intake during treatment can cause dilutional hyponatraemia, seizure or cerebral oedema. Diagnostic administration must be supervised and interpreted with urine osmolality.

Prostaglandin inhibition can reduce urine volume, but this physiological effect rarely justifies routine long-term exposure in adults.

NSAID therapy

Avoid routine chronic use; if an exceptional specialist indication exists, use the minimum effective licensed dose for the shortest planned period with gastroprotection assessment.

AKI, papillary injury, sodium retention, hypertension, gastrointestinal bleeding and cardiovascular events are important, particularly in CKD or dehydration.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Hypernatraemic neurological injury

Unreplaced free-water loss raises plasma tonicity, causing lethargy, irritability, confusion, seizures and potentially permanent neurological harm.

Hypovolaemia and AKI

Severe polyuria can reduce circulating volume, causing hypotension, renal hypoperfusion and acute kidney injury that further complicates medicine handling.

Lithium toxicity feedback

Dehydration and falling filtration can raise lithium exposure, worsening neurological toxicity and tubular dysfunction unless medicine and fluid status are reviewed together.

Growth and daily-function impairment

Congenital disease can cause poor growth and recurrent childhood illness, while chronic thirst, nocturia and sleep disruption substantially impair adult daily life.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Track measured urine volume, thirst, nocturia, body weight and the practical reliability of day-and-night water access.
Repeat sodium, potassium, creatinine and osmolality after acute illness and after starting a thiazide, amiloride or any solute-reduction plan.
For lithium, follow current NICE and SPS schedules for trough levels, eGFR, urea and electrolytes, calcium and thyroid function, increasing frequency when renal risk changes.
In children or dependent adults, maintain a written emergency water-replacement plan for fasting, procedures, vomiting and carers or school.
Monitor nutrition and growth when sodium and protein intake are modified, using a renal dietitian rather than unsupervised restriction.
Revisit genetic counselling, carrier testing and reproductive options for confirmed AVPR2 or AQP2 disease as family circumstances change.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Normal sodium can coexist

An alert patient with intact thirst may replace enormous renal water losses and keep sodium normal until access is interrupted.

Frequency is not polyuria

Cystitis, overactive bladder and obstruction cause frequent small voids, whereas DI requires genuinely increased daily water volume.

Lithium decisions are shared

The renal diagnosis does not by itself determine cessation; psychiatric history, alternatives, toxicity and reversibility all shape the plan.

Thiazides require lithium caution

The same medicine that lowers urine volume can reduce lithium clearance and provoke toxicity unless dosing and levels are actively coordinated.

Water deprivation can harm

A person unable to concentrate urine may become rapidly hypernatraemic, making protocol-led supervision and stopping criteria essential.

11Common pitfallsFrequent interpretation and management errors.

01
Diagnosing DI from urinary frequency without confirming a high 24-hour volume and dilute urine.
02
Reassuring from a normal sodium when the patient is drinking continuously to compensate for severe renal losses.
03
Performing an unsupervised water-deprivation test at home or on a ward without defined monitoring and stopping criteria.
04
Stopping lithium abruptly without mental-health input or failing to check for interacting medicines and toxicity.
05
Prescribing a thiazide to a lithium user without anticipating a rise in lithium concentration.
06
Using chronic NSAIDs casually in a patient already vulnerable to dehydration and kidney injury.
07
Assuming desmopressin treats all forms of diabetes insipidus and overlooking renal resistance.