Physical Examination of urine (Part -1)

A Routine Urine Examination (RUE) is a fundamental diagnostic test used to assess the health of the kidneys, urinary tract, and other systemic conditions. It involves three main components: physical, chemical, and microscopic examinations.
Each component provides essential information about the urine’s characteristics and its clinical significance.
Urine is a liquid waste product produced by the kidneys during blood filtration. It is key in eliminating waste and maintaining the body’s water and electrolyte balance.
The composition of urine is mostly water, but it also contains various organic and inorganic substances, depending on factors such as diet, health, hydration status, and metabolic activity.

Table of contents

Components of Urine:

1. Water (95-96%)

2. Organic Substances (2-4%)

Uric Acid
Creatinine
Urea
Amino acids
Hormones
Carbohydrates

3. Inorganic Substances in Urine (1-2%)

Sodium (Na⁺)
Potassium (K⁺)
Chloride (Cl⁻)
Calcium (Ca²⁺)
Magnesium (Mg²⁺)
Phosphate (PO₄³⁻)
Sulfate (SO₄²⁻)
Ammonium (NH₄⁺)
Bicarbonate (HCO₃⁻)
Oxalate (C₂O₄²⁻)
Fluoride (F⁻)

Physical Examination of urine:

1. Color of Urine:

Urine colour is a key indicator of hydration and can also reflect the presence of certain substances or diseases.

Normal Color:
- The normal colour of urine is pale yellow to amber, which comes from a pigment called urochrome. The colour can vary depending on the concentration of the urine. Lighter-coloured urine usually indicates better hydration, while darker-yellow urine suggests dehydration.
Abnormal Colours:
- Dark yellow or amber: May indicate dehydration or excessive sweating.
- Red or pink: Often due to the presence of blood (hematuria), but it can also result from consuming certain foods (e.g., beets) or medications (e.g., rifampin).
- Brown: May suggest liver disease or the presence of bile pigments, such as in jaundice. Certain medications can also cause brown urine.
- Orange: This can be due to dehydration or consuming foods rich in carotene, and medications like phenazopyridine can cause it.
- Blue or green: Rare, but can be caused by bacterial infections (e.g., Pseudomonas) or medications (e.g., methylene blue).
- Milky or cloudy: Often indicates the presence of pus, bacteria, or crystals, suggesting infection or kidney stones.

2. Clarity (Turbidity):

Urine clarity, or turbidity, measures how clear or cloudy the urine is.

Clear Urine:

- Normal urine should be clear. This reflects a healthy urinary system with no significant presence of cells, crystals, or bacteria.

Cloudy or Turbid Urine:

- Pus (pyuria): Cloudiness may indicate the presence of white blood cells (WBCs) due to infection, commonly a urinary tract infection (UTI).
- Bacteria: A bacterial infection may cause cloudy urine, which can often be confirmed with chemical and microscopic analysis.
- Crystals: Urine may appear cloudy when certain crystals (e.g., urates, phosphates) precipitate out of the urine.
- Proteinuria: The presence of protein, especially in high amounts, can give the urine a frothy or foamy appearance.
- Lipids: Lipiduria (fats in urine) can cause a milky appearance, which may be seen in conditions like nephrotic syndrome.

3. Odour of Urine:

Normal Odour:

- Urine has a mild, characteristic odour due to the presence of waste products like urea.

Foul or Strong Odour:

- Urinary Tract Infection (UTI): A strong, foul-smelling odour is often associated with bacterial infections.
- Dehydration: When urine is highly concentrated, it may have a stronger odour due to the increased concentration of waste products.
- Ketosis (Fruity Odour): In conditions such as diabetic ketoacidosis (DKA) or during prolonged fasting, the body breaks down fats for energy, resulting in the production of ketones, which give the urine a fruity or sweet smell.
- Food and Medication: Certain foods, like asparagus or garlic, and medications, like antibiotics, can impart a strong or unusual odour to the urine.

4. Specific Gravity:

Normal Range:

- Normal specific gravity ranges from 1.005 to 1.030. It provides insight into how well the kidneys regulate water balance and concentrate urine.

Low Specific Gravity (Hyposthenuria):

- Specific gravity lower than 1.005 may indicate dilute urine, which can occur in:
  - Excessive fluid intake (overhydration).
  - Diabetes insipidus, where the kidneys fail to reabsorb water due to a deficiency of antidiuretic hormone (ADH).
  - Renal failure, where the kidneys lose the ability to concentrate urine.

High Specific Gravity (Hypersthenuria):

- Specific gravity higher than 1.030 indicates concentrated urine, which can occur in:
  - Dehydration or decreased fluid intake.
  - Diabetes mellitus, where excess glucose in the blood spills into the urine, increasing solute concentration.
  - Heart failure, where the body retains more water, leading to concentrated urine.
  - Shock or burns, causing fluid loss and thus concentrating the urine.

5. Volume:

Normal urine
- The total amount of urine produced is typically over 24 hours.
- Ranges from 1,000 to 2,000 mL/day (1-2 litres), with variations based on fluid intake, diet, and kidney
Abnormal Urine Volumes:

- Polyuria: Increased urine output above 2,500 mL/day, common in diabetes and excessive fluid intake.
- Oliguria: Decreased output below 400 mL/day, in dehydration or kidney issues.
- Anuria: Very low output under 100 mL/day, indicating severe kidney failure or obstruction.
- Nocturia: Frequent night-time urination, often due to conditions like heart failure or prostate issues.

6. pH:

The normal range of urine pH is typically 4.5 to 8.0, with an average around 6.0 (slightly acidic).

Factors Affecting Urine pH:

1. Diet:

- - High-protein diets (meat, eggs) tend to produce acidic urine (lower pH).
  - Vegetarian diets and high fruit consumption often result in more alkaline urine (higher pH).

1. Medications:

- - Certain drugs (e.g., sodium bicarbonate) can make urine more alkaline, while others (e.g., ammonium chloride) may acidify it.

1. Metabolic and Respiratory Conditions:

- - Acidosis (metabolic or respiratory) can cause acidic urine.
  - Alkalosis (metabolic or respiratory) can lead to more alkaline urine.

Clinical Significance of Urine pH:

1. Acidic Urine (pH < 5.5):

- - May indicate metabolic acidosis, diabetic ketoacidosis, or a diet high in animal protein.
  - Can be associated with kidney stones (e.g., uric acid or cystine stones).

1. Alkaline Urine (pH > 7.5):

- - Can suggest urinary tract infections (UTIs) caused by bacteria that produce urease, which breaks down urea into ammonia, making the urine more alkaline.
  - Common in patients with metabolic alkalosis, a diet rich in fruits and vegetables, or after taking certain medications.
  - May contribute to the formation of struvite stones.