Endoscopic trans-sphenoidal surgery has become the standard approach for pituitary tumors. Despite advances in technique, disorders of water balance, particularly diabetes insipidus (DI), remain common postoperative complications. (Hensen et al., 2013; Nemergut et al., 2012)

Central DI results from impaired secretion of arginine vasopressin (AVP) due to injury to hypothalamic neurons or the pituitary stalk.

The reported incidence ranges widely from 1% to 67%, depending on diagnostic criteria and surgical factors.  (Almalki et al., 2021; Woods & Thompson, 2008)

Although most cases are transient, a subset progresses to permanent DI, significantly impacting long-term quality of life.

METHODS

A systematic literature review was performed using databases including PubMed, Scopus, and Science Direct. Keywords included:

• “diabetes insipidus”
• “pituitary surgery”
• “endoscopic transsphenoidal”
• “postoperative polyuria”

Inclusion criteria:

• Studies on postoperative DI after pituitary/suprasellar surgery
• Reviews, clinical studies, and guidelines
• English-language publications

Exclusion criteria:

• Non-surgical DI
• Animal studies

All together 335 records were identified through database searching out of which 15 studies were included in quantitative synthesis (Fig 1). Table 1 depicts the characteristics of all included studies.

Figure 1: Study selection - PRISMA flow Diagram

Table 1: Characteristics of included studies.

Pathophysiology

AVP is synthesized in the supraoptic and paraventricular nuclei and transported to the posterior pituitary. Surgical injury disrupts this pathway, leading to impaired water reabsorption.  (Freda et al., 2011)

Three postoperative patterns are described:

1. Transient DI (most common)
2. Permanent DI
3. Triphasic response:  (Woods & Thompson, 2008)
• Phase 1: Early DI
• Phase 2: SIADH (hyponatremia)
• Phase 3: Permanent DI

Risk factors include:

• Large tumors
• Craniopharyngioma or Rathke’s cleft cyst
• Stalk manipulation or transection
• CSF leak during surgery

Diagnosis

Clinical Features

• Polyuria (>3 L/day or >200–300 mL/hour)
• Polydipsia
• Signs of dehydration

DI is characterized by large volumes of dilute urine with rising plasma osmolality.

Diagnostic Criteria

Typical criteria include:

• Urine output >3 mL/kg/hr
• Urine osmolality <300 mOsm/kg
• Serum sodium >145 mmol/L
• Serum osmolality >295 mOsm/kg

Differential Diagnosis

Postoperative polyuria may result from:

• Osmotic diuresis (hyperglycemia)
• Excess IV fluids
• Diuretics or mannitol
• Cerebral salt wasting
• SIADH (later phase)

Careful evaluation is essential before labelling DI.

Monitoring (De Vries et al., 2020; Hannon et al., 2012)

• Hourly urine output
• Serum sodium (4–6 hourly initially)
• Fluid balance charting

Management

General Principles

The goal is to maintain fluid and electrolyte balance and avoid complications such as hypernatremia or hyponatremia.

1. Conservative Management

• Encourage oral water intake (if thirst intact)
• Close monitoring only in mild cases  (De Vries et al., 2020; Hannon et al., 2012)

Many cases are self-limiting and require no pharmacologic treatment.

2. Fluid Replacement

• Match urine output with hypotonic fluids
• Avoid rapid correction of sodium

3. Desmopressin Therapy (Almalki et al., 2021; Nemergut et al., 2012)

Indications:

• Persistent polyuria
• Hypernatremia
• Inability to maintain hydration

Desmopressin (DDAVP): (Almalki et al., 2021; Nemergut et al., 2012)

• Intranasal, oral, or IV
• Titrate to avoid water intoxication

Vasopressin analogues effectively normalize urine output and serum sodium.

4. Management of Special Situations

Adipsic DI

• Impaired thirst mechanism
• Requires scheduled fluid intake and strict monitoring  (De Vries et al., 2020; Hannon et al., 2012)
• Associated with high morbidity

5. Long-term Management

• Distinguish transient vs permanent DI
• Educate patients on:
• Fluid intake
• Desmopressin use  (Almalki et al., 2021; Nemergut et al., 2012)
• Warning signs of hyponatremia

Complications

• Hypernatremia
• Hyponatremia (especially during SIADH phase)
• Volume depletion
• Increased morbidity if untreated

Hyponatremia occurs in up to 13–35% of patients post-surgery.

DISCUSSION

DI after endoscopic pituitary surgery remains a clinically significant but manageable complication. Variability in reported incidence reflects heterogeneity in diagnostic definitions and perioperative protocols.

Early differentiation from other causes of postoperative polyuria is crucial. Standardized diagnostic criteria and protocols for monitoring sodium and urine output can improve outcomes. (De Vries et al., 2020; Hannon et al., 2012)

Desmopressin remains the cornerstone of therapy, but judicious use is essential to prevent iatrogenic hyponatremia. (Almalki et al., 2021; Nemergut et al., 2012)

Future directions include:

• Standardized definitions
• Predictive models for DI risk
• Enhanced intraoperative preservation techniques

CONCLUSION

Postoperative DI is common after endoscopic pituitary surgery but is usually transient. Early diagnosis, careful monitoring, and individualized treatment are key to preventing complications and improving patient outcomes.

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