“Melanosis” in the small and large intestine

Abstract

Deposition of pigment in the intestinal mucosa is commonly observed by the endoscopist, especially within the colon, and particularly during investigations for constipation. Pigment may also be detected in the small intestine. Although labeled as melanosis, electron microscopy and X-ray analytical methods have provided evidence that this pigment is not melanin at all, but lipofuscin. Often, herbal remedies or anthracene containing laxatives are often historically implicated, and experimental studies in both humans and animal models have also confirmed the intimate relationship with these pharmacological or pseudo-pharmacological remedies. The appearance of melanosis coli during colonoscopy is largely due to pigment granule deposition in macrophages located in the colonic mucosa. The pigment intensity is not uniform, being more intense in the cecum and proximal colon compared to the distal colon. Possibly, this reflects higher luminal concentrations of an offending agent in the proximal compared to distal colon, differential absorption along the length of the colon, or finally, differences in macrophage distribution within the colon. Mucosal lymphoid aggregates normally display a distinct absence of pigment producing a "starry sky" appearance, especially in the rectosigmoid region. Interestingly, some focal, usually sessile, colonic mucosal neoplastic lesions, rather than submucosal lesions, may be better appreciated as pigment deposition may be absent or limited. If detected, removal and further histopathologic analysis of the polyp may be facilitated.

Colon Melanosis in a 15-Year-Old Child: Clinical Observation

“…Обращает на себя внимание неравномерная интенсив-ность пигментации, наиболее выраженная в слепой киш-ке и проксимальных отделах толстой кишки [3,[7][8][9]. Этот факт связывают с концентрацией в просвете прокси-мального отдела толстой кишки большого количества повреждающего вещества, например слабительного пре-парата или его производных.…”

“…Другой возможной при-чиной может выступать разная абсорбирующая способ-ность отделов толстой кишки. Наконец, имеют значение особенности топографического распределения макро-фагов в толстой кишке [3,8]. Лимфоидные фолликулы, в норме представленные в слизистой оболочке, при меланозе не накапливают пигмент, поэтому ткань при-обретает вид «звездного неба», особенно в ректосигмо-идном отделе толстой кишки.…”

“…К такому состоянию чаще всего приводит неконтролируемый прием нестеро-идных противовоспалительных средств или слабитель-ных препаратов, содержащих антрагликозид. Меланоз кишки может быть диагностирован при заболеваниях печени и поджелудочной железы, раке толстой кишки [3][4][5]. При резко выраженном меланозе пигментация локализуется не только в толстой, но и в тонкой кишке вплоть до брыжеечных лимфатических узлов [2].…”

Evidence of Oxidative Injury in Pigs With Melanosis Coli

“…7 Histochemical staining reactions of the pigment-laden macrophages in the lamina propria of human cases have demonstrated granule composition is not consistent with melanin pigment. 6 As a result, it has been suggested that pseudomelanosis coli may be a more appropriate name; 9 however, others refute this as an erroneous term, which means ''false black'' or ''not black,'' and suggest that melanosis coli is appropriate regardless of the pigment type. 5 Accordingly, for consistency, the authors have chosen to use the term melanosis coli to describe the discolored colorectal tissues in swine.…”

“…6,8 Histologically, melanosis coli is characterized by accumulations of pigment-laden macrophages in the lamina propria of the colorectal mucosa. 7 Histochemical staining reactions of the pigment-laden macrophages in the lamina propria of human cases have demonstrated granule composition is not consistent with melanin pigment.…”