science

Oliguria

Oliguria is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Oliguria rather than just read about it. In short: Oliguria or hypouresis is the low output of urine: specifically, more than 80 ml/day, but less than 400ml/day. The decreased output of urine may be a sign of dehydration, kidney failure, hypovolemic shock, hyperosmolar hyperglycemic nonketotic syndrome (HHNS), multiple organ dysfunction syndrome, urinary obstruction/urinary retention, diabetic ketoacidosis (DKA), pre-eclampsia, and urinary tract infections, among ot…

Key takeaways

Oliguria belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Oliguria to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Oliguria from memory before moving on to harder problems.

Reference excerpt

Oliguria or hypouresis is the low output of urine: specifically, more than 80 ml/day, but less than 400ml/day. The decreased output of urine may be a sign of dehydration, kidney failure, hypovolemic shock, hyperosmolar hyperglycemic nonketotic syndrome (HHNS), multiple organ dysfunction syndrome, urinary obstruction/urinary retention, diabetic ketoacidosis (DKA), pre-eclampsia, and urinary tract infections, among other conditions. Beyond oliguria is anuria, which represents an absence of urine, clinically classified as below 80 or 100 ml/day. The term oliguria is derived from oligo-meaning "small, little," + -uria, from the Greek word ouron, meaning "urine".

Definition Oliguria is defined as a urine output that is less than 1 mL/kg/h in infants, less than 0.5 mL/kg/h in children, and less than 400 mL or 500 mL per 24h in adults - this equals 17 or 21 mL/hour. For example, in an adult weighing 70 kg it equals 0.24 or 0.3 mL/kg/h. Alternatively, however, the value of 0.5 mL/kg/h is commonly used to define oliguria in adults as well.

Diagnostic approach Perform ultrasound examination of the kidney to rule out obstructive processes. The mechanisms causing oliguria can be categorized globally in three different categories:

Prerenal: in response to hypoperfusion of the kidney (e.g. as a result of dehydration by poor oral intake, cardiogenic shock, diarrhoea, G6PD deficiency, massive bleeding or sepsis) Renal: due to kidney damage (severe hypoperfusion, rhabdomyolysis, medication) Postrenal: as a consequence of obstruction of the urine flow (e.g. enlarged prostate, tumour compression urinary outflow, expanding hematoma or fluid collection)

Postoperative oliguria Patients usually have a decrease in urine output after a major operation that may be a normal physiological response to:

fluid/ blood loss – decreased glomerular filtration rate secondary to hypovolemia and/or hypotension response of adrenal cortex to stress-increase in aldosterone (Na and water retention) and antidiuretic hormone (ADH) release

Babies Oliguria, when defined as less than 1 mL/kg/h, in infants is not attributed to kidney failure.

See also Polyuria (excessive urine production) Anuria (absolute lack of urine output) Intra-abdominal hypertension (IAH) and Abdominal Compartment Syndrome (ACS)

References

External links

Worked examples

Example 1 — a first encounter with Oliguria

Start with the simplest possible case. Write down what Oliguria claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Oliguria before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Oliguria ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Oliguria

In research: Oliguria appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Oliguria in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Oliguria is common in secondary-school and first-year university syllabi. It links to neighbouring topics Symptoms and signs: Urinary system, so understanding it makes those chapters shorter.
In everyday life: Look for Oliguria outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Oliguria in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Oliguria means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Oliguria out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Oliguria in simple terms?

Why does Oliguria matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Oliguria?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Oliguria.