Confirming irritable bowel syndrome
Under the Rome IV criteria, irritable bowel syndrome (IBS) requires recurrent abdominal pain on average at least 1 day a week in the last 3 months, associated with two or more of the following: related to defecation, associated with a change in stool frequency, or associated with a change in stool form. Symptom onset must be at least 6 months before diagnosis. She has pain about twice a week that eases after defecation and comes with looser, more frequent stools, and her symptoms began 7 months ago. She meets the criteria.
Assigning the subtype
The IBS subtype is based on stool form on days with abnormal bowel movements, often described using the Bristol Stool Form Scale. IBS with predominant diarrhea (IBS-D) applies when more than 25% of abnormal bowel movements are loose or watery and less than 25% are hard or lumpy. Her loose stools make up about 40% of bowel movements, and none are hard or lumpy. Loose stools above the 25% threshold with almost no hard stools define the diarrhea-predominant subtype.
| Subtype | Loose or watery stools | Hard or lumpy stools |
|---|
| IBS-D (diarrhea) | More than 25% | Less than 25% |
| IBS-C (constipation) | Less than 25% | More than 25% |
| IBS-M (mixed) | More than 25% | More than 25% |
| IBS-U (unclassified) | Meets IBS criteria but no subtype pattern | |
Why the other options are wrong
The mixed subtype requires both hard and loose stools above the threshold; she has had no hard stools. The unclassified subtype is used when stool form does not fit any of the defined patterns, which is not the case here. The claim that 12 months are needed reflects older criteria; Rome IV requires 3 months of symptoms with onset at least 6 months before diagnosis. Watch out! Questions about IBS subtypes often hinge on whether the client has any hard stools at all.
Exam takeaway
First confirm the IBS criteria (pain frequency, relation to defecation or stool change, duration and onset), then assign the subtype by stool form. Before accepting a functional diagnosis, the nurse also checks for alarm features such as anemia, bleeding, weight loss, or nocturnal symptoms. Key point! Rome IV IBS needs pain at least 1 day a week for 3 months, onset 6 months earlier, and subtype is set by the proportion of loose versus hard stools.