In pathology, distal is a location word. It describes a part of the body, an organ, or a tissue sample that is farther away from a reference point. Depending on what is being described, that reference point is either the center of the body or the place where a structure begins. The opposite of distal is proximal, which means closer to the center of the body or to where a structure begins. Distal and proximal describe position only. Neither is a diagnosis, and neither says anything on its own about whether a finding is normal or abnormal. This article explains what distal means, how it is used to describe organs and specimens, and where you are likely to see it on a pathology report.
How is the term “distal” used?
Distal is used in two closely related ways, and in both the opposite term is proximal:
- For arms and legs — Distal means farther from where the limb joins the body. For example, the hand is distal to the elbow, and the fingertips are the most distal part of the hand.
- For tube-shaped organs — In organs such as the colon, esophagus, stomach, and bile ducts, distal means farther along the tube from where it begins, toward its far end. Importantly, this does not necessarily mean farther from the center of the body. The distal end of the colon, for example, is the rectum, which actually sits deep in the pelvis.
The colon is a helpful example. It begins where it joins the small bowel and travels through the abdomen before ending at the rectum and anus. Its parts, in order, are the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum. The sigmoid colon and rectum make up the distal colon because they are farthest along the tube from where it begins. If a pathologist examined the entire colon, the rectum would be the most distal part.
Distal can also describe part of a specimen even when only a portion of an organ is removed. For example, if the sigmoid colon and rectum are removed together, the sigmoid colon end is the proximal part of the specimen, and the rectum end is the distal part.
What is a distal margin?
One of the most common places you will see the word distal on a pathology report is in the description of margins. When a segment of a tube-shaped organ is removed by surgery (a resection), the pathologist examines the cut edges, called margins, to check whether disease reaches them. The two ends of the removed segment are labeled by position: the proximal margin is the cut edge at the beginning end, and the distal margin is the cut edge at the far end. In a segment of colon removed for cancer, for example, the distal margin is the edge closer to the rectum.
- Negative distal margin — No abnormal or tumor cells reach the distal edge, which suggests the abnormal area was fully removed at that end.
- Positive distal margin — Abnormal or tumor cells reach the distal edge, which suggests some abnormal tissue may remain at that end and may influence decisions about further treatment.
Because distal simply tells you which edge is being described, it helps you locate exactly where on the specimen a positive or negative margin was found.
Questions to ask your doctor
- Which part of my organ or specimen does “distal” refer to on my report?
- Was the distal margin negative (clear) or positive?
- If the distal margin was positive, what does that mean for my treatment?
- How does the distal part of my specimen compare with the proximal part?
- Does the location of the finding, distal versus proximal, affect my follow-up?
- Can you show me on a diagram where the distal area is?
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