Unit 2: Diagnostic Methods used for Sputum, Urine and Stool Analysis

Table of Contents

1. Sputum Analysis

Sputum is mucus secreted from the lower respiratory tract (lungs and bronchi). It is not saliva. A sputum analysis is crucial for diagnosing respiratory diseases, especially infections.

Sample Collection: The best sample is a deep cough specimen collected first thing in the morning, as it is more concentrated. The patient should rinse their mouth with water first to avoid contamination with food or saliva.

Physical Characteristics (Macroscopic)

Characteristic Normal Abnormal Constituents & Indication
Volume Very small amount Large volume (>100ml/day): Suggests lung abscess, bronchiectasis, or advanced tuberculosis.
Colour Clear, white/opaque Yellow-Green (Purulent): Presence of pus (neutrophils); indicates infection (pneumonia, bronchitis).
Rusty Red: Presence of old blood; common in pneumococcal pneumonia.
Bright Red (Haemoptysis): Fresh blood; indicates tuberculosis, lung cancer, or lung abscess.
Pink & Frothy: Pulmonary oedema (heart failure).
Consistency Mucoid (viscous) Thick & Tenacious: Asthma, cystic fibrosis.
Watery/Frothy: Pulmonary oedema.
Odour Odourless Foul/Putrid: Anaerobic bacterial infection (e.g., lung abscess).

Microscopic Analysis (Abnormal Constituents)

2. Urine Analysis (Urinalysis)

Urinalysis is a fundamental test that provides insights into kidney function and systemic diseases (like diabetes).

Physical Characteristics (Macroscopic)

Characteristic Normal Abnormal Constituents & Indication
Colour Pale yellow to deep amber (due to urochrome pigment) Dark Red/Brown: Presence of blood (haematuria) or haemoglobin.
Dark Yellow/Brown-Green: Presence of bilirubin (liver disease).
Cloudy/Turbid: Presence of pus, bacteria, or crystals (infection, kidney stones).
pH Slightly acidic (avg. 6.0, range 5.5-6.5) High pH (Alkaline): Urinary tract infection (UTI) (bacteria convert urea to ammonia), or vegetarian diet.
Low pH (Acidic): High protein diet, acidosis.
Specific Gravity (SG) 1.012 – 1.024 Measures the kidney's concentrating ability.
High SG: Dehydration, diabetes mellitus (due to glucose).
Low SG: Overhydration, chronic kidney disease (kidneys can't concentrate urine).

Chemical Analysis (Abnormal Constituents)

These are typically tested using a "dipstick".

3. Stool Analysis

Stool analysis is essential for diagnosing gastrointestinal (GI) disorders, including infections, poor nutrient absorption, and cancer.

Physical Characteristics (Macroscopic)

Characteristic Normal Abnormal Constituents & Indication
Colour Brown (due to bilirubin/bile) Black, Tarry: Digested blood from upper GI bleeding (e.g., stomach ulcer).
Bright Red: Fresh blood from lower GI bleeding (e.g., haemorrhoids).
Clay-Coloured/Pale: Lack of bile; indicates biliary obstruction (gallstones, liver disease).
Consistency Soft and formed (Bristol Stool Scale Type 3-4) Watery: Diarrhoea (e.g., infection, inflammation).
Hard, pellet-like: Constipation.
Mucus Small amount is normal Copious mucus or bloody mucus: Abnormal. Indicates inflammation (e.g., dysentery, inflammatory bowel disease).

Microscopic Analysis (Abnormal Constituents)

Practical Component: Detection in Urine

This is performed using a Urine Dipstick, which is a plastic strip with small square-colored fields.

Procedure:

  1. Collect a midstream urine sample in a clean container.
  2. Dip the test strip into the urine, ensuring all colored fields are submerged, for a few seconds.
  3. Remove the strip and tap it on the side of the container to remove excess urine.
  4. Wait for the specified time (e.g., 30-60 seconds) for the results to appear.
  5. Compare the colors of the fields on the strip to the color chart on the bottle.

Detection: