Mees lines or Aldrich–Mees lines, also called leukonychia striata, are white lines of discoloration across the nails of the fingers and toes (leukonychia). Presentation
They are typically white bands traversing the width of the nail. As the nail grows they move towards the end, and finally disappear when trimmed. Causes
Mees lines appear after an episode of poisoning with arsenic, thallium or other heavy metals or selenium, opioid MT-45, and can also appear if the subject is suffering from kidney failure. They have been observed in chemotherapy patients. Eponym and history
Although the phenomenon is named after Dutch physician R. A. Mees, who described the abnormality in 1919, earlier descriptions of the same abnormality were made by Englishman E. S. Reynolds in 1901 and by American C. J. Aldrich in 1904. See also
Leukonychia
List of cutaneous conditions
Muehrckes nails – a similar condition, except the lines are underneath the nails and so do not move as the nail grows

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A colorectal polyp is a polyp (fleshy growth) occurring on the lining of the colon or rectum. Untreated colorectal polyps can develop into colorectal cancer.Colorectal polyps are often classified by their behaviour (i.e. benign vs. malignant) or cause (e.g. as a consequence of inflammatory bowel disease). They may be benign (e.g. hyperplastic polyp), pre-malignant (e.g. tubular adenoma) or malignant (e.g. colorectal adenocarcinoma). Signs and symptoms
Colorectal polyps are not usually associated with symptoms. When they occur, symptoms include bloody stools; changes in frequency or consistency of stools (such as a week or more of constipation or diarrhoea); and fatigue arising from blood loss. Anemia arising from iron deficiency can also present due to chronic blood loss, even in the absence of bloody stools. Another symptom may be an increased mucus production especially those involving villous adenomas. Copious production of mucous causes loss of potassium that can occasionally result in symptomatic hypokalemia. Occasionally, if a polyp is big enough to cause a bowel obstruction, there may be nausea, vomiting and severe constipation. Structure
Polyps are either pedunculated (attached to the intestinal wall by a stalk) or sessile (grow directly from the wall). : 1342   In addition to the gross appearance categorization, they are further divided by their histologic appearance as tubular adenoma which are tubular glands, villous adenoma which are long finger like projections on the surface, and tubulovillous adenoma which has features of both.