Dehydration and fluid overload !

Syndrome

Too little fluid (thirst, dry mouth, little urine) or too much (swelling, breathlessness): the exam helps tell them apart.

Updated 2026-11-01

See it in 3D: Kidneys · Internal jugular vein · External jugular vein · Inferior vena cava · Skin

What it is

Volume status is judged at the bedside from vital signs, skin and mucosa, neck veins, lungs, edema, urine output and weight. Dehydration (hypovolemia) and fluid overload have opposite findings but can coexist: a patient can be edematous and still have too little volume inside the vessels. In children, dehydration from diarrhea remains a major cause of preventable death.

Key findings

Current weight versus previous weight.
Heart rate, lying and standing blood pressure, capillary refill.
Mucosa, tears, eyes, the fontanelle in infants and skin pinch.
Jugular veins and hepatojugular reflux.
Lungs (crackles, effusion), peripheral edema and ascites.
Urine output and color; mental state.

Pathophysiology

Body water is split between the intracellular and extracellular spaces; the extracellular space includes plasma and interstitial fluid.
Between capillary and interstitium, fluid moves according to hydrostatic pressure (pushes it out) and the oncotic pressure of albumin (holds it in).
Loss of extracellular fluid lowers venous return and cardiac output: tachycardia, vasoconstriction and, when these run out, hypotension; the kidney conserves water and sodium and urine falls.
Edema appears when hydrostatic pressure rises (heart failure, overload) or oncotic pressure falls (cirrhosis, nephrotic syndrome); in the latter, intravascular volume may be low.
A kidney that filters poorly (acute kidney injury or chronic kidney disease) cannot excrete excess sodium and water.

Dehydration vs fluid overload

Finding	Dehydration	Fluid overload
Weight	Falls	Rises
Pulse and pressure	Tachycardia, orthostatic hypotension	Normal or high pressure; tachycardia possible
Neck veins	Flat	Distended, hepatojugular reflux
Mucosa and skin	Dry, slow skin pinch, slow capillary refill	Moist, pitting edema
Lungs	Clear	Crackles, pleural effusion
Urine	Scant and dark	Variable; scant if the cause is renal

Common causes

Dehydration: diarrhea and vomiting (gastroenteritis, cholera), fever, heavy sweating, burns, diuretics, hyperglycemia with osmotic diuresis and poor intake in older adults or patients with reduced consciousness.
Overload: heart failure, acute kidney injury and chronic kidney disease, cirrhosis, nephrotic syndrome and excess intravenous fluids.
Edema with low circulating volume: cirrhosis, nephrotic syndrome, sepsis with capillary leak and malnutrition.

Tests that confirm it

Sodium, potassium, urea and creatinine; the urea-to-creatinine ratio rises in dehydration.
Urine specific gravity and urine sodium.
Bedside ultrasound (inferior vena cava, lung B-lines) and natriuretic peptides when heart failure is suspected.

Test yourself

Think of the answer, then tap the question to see it.

Which signs of dehydration are looked for in an infant?

Sunken eyes, crying without tears, dry mouth and tongue, a sunken fontanelle, slow skin-pinch recoil, few wet diapers, irritability or lethargy.

Why can a patient with cirrhosis be edematous yet have too little volume inside the vessels?

Low albumin lowers oncotic pressure, so fluid escapes into the interstitium and peritoneum and effective intravascular volume falls.

What is the most useful measure for following volume changes from day to day?

Daily weight, taken at the same time, on the same scale and in similar clothing, together with the fluid balance.

Which neck and chest findings suggest fluid overload?

Raised jugular venous pressure, a positive hepatojugular reflux, lung crackles, a third heart sound and pleural effusion.

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See it in 3D

The structures of Durgical's 3D anatomy where it is found.

← All of the clinical exam

Educational content on the clinical exam; it is learned and practised under supervision. It does not replace assessment by a health professional and is not for self-diagnosis.

Sources: Dehydration: MedlinePlus (MedlinePlus, U.S. National Library of Medicine, 2026); 26.1 Body Fluids and Fluid Compartments (OpenStax, Rice University, 2022).

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Representative model, for educational purposes only.