Abnormal Stool Causes of Changes in Color, Shape, Volume

The color, volume and consistency or shape of stool varies from person to person. It is generally accepted that the normal stool is :

  • tan to dark brown in color
  • firm but soft
  • elongated like a sausage
  • passed at least 3 times a week
  • volume of less than 200 ml or 200g per day

Abnormal Stool Colors

Normal bowel movement color may vary between different shades of brown. Stool may also be reported as being yellow-brown in color. The typical color of stool is due to stercobilin and urobilin, two derivatives of bilirubin, which are transformed by air and bacteria in the gut.

Foods and drinks with strong colorants and dyes should first be excluded as a possible cause of changes in stool color.

  • Red Stool
    • Beets (soup, juice)
    • Artificially colored foods or drinks like jelly and concentrate juices
    • Fresh blood in the stool (hematochezia) – intraintestinal, hemorrhoids, anal fissures

The causes of other changes in stool color are discussed under the respective articles.

Abnormal Stool Shape and Consistency

The Bristol Stool Chart (below) defines 7 types of stool which may be seen in normal and abnormal bowel movements. This is discussed further under the different types of feces. About 70% to 75% of stool weight is due to water and the remaining amount is solid matter composed of a number of constituents as discussed under Feces Composition.

  • Types 1 and 2 : hard stool, dry stool, constipated stool, hard balls or nuts, lumpy
  • Types 3 and 4 : normal stool, soft, sausage-shaped
  • Types 5, 6, 7 : loose stool, watery stool, diarrhea stool, fluffy, uneven, blobs, poorly formed

Picture from Wikimedia Commons

Abnormal Bowel Movement – Amount and Frequency

The frequency of bowel movement and quantity of stools passed may vary among individuals. The normal amount and frequency of bowel movement lies between the disordered states of constipation and diarrhea.

  • Constipation
    • less than 3 bowel movements in a week
    • straining and difficulty passing stool
  • Diarrhea
    • more than 3 bowel movements in a day
    • more than 200ml or 200g of stool in a day

Therefore the amount and frequency of normal bowel movement can be defined as a bowel movement at least 3 times a week, but not exceeding 3 times a day with a total daily volume that is less than 200ml or 200g.

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