Page 595 - Textbook of Pathology, 6th Edition

Thus, there is good correlation between macroscopic PSEUDOMYXOMA PERITONEI. Pseudomyxoma peritonei 579
and microscopic findings in acute appendicitis. is appearance of gelatinous mucinous material around the
appendix admixed with epithelial tumour cells. It is generally
CLINICAL COURSE. The patient presents with features of due to mucinous collection from benign mucinous
acute abdomen as under: cystadenoma of the ovary or mucin-secreting carcinoma of
1. Colicky pain, initially around umbilicus but later localised the appendix.
to right iliac fossa ADENOCARCINOMA. It is an uncommon tumour in the
2. Nausea and vomiting appendix and is morphologically similar to adenocarcinoma
3. Pyrexia of mild grade elsewhere in the alimentary tract.
4. Abdominal tenderness
5. Increased pulse rate
6. Neutrophilic leucocytosis. LARGE INTESTINE
An attack of acute appendicitis predisposes the appendix
to repeated attacks (recurrent acute appendicitis) and thus NORMAL STRUCTURE
surgery has to be carried out. If appendicectomy is done at a
later stage following acute attack (interval appendicectomy), The large bowel consists of 6 parts—the caecum, ascending
pathological changes of healing by fibrosis of the wall and colon, transverse colon, descending colon, sigmoid colon and
chronic inflammation are observed. rectum, and in all measures about 1.5 meters in length. The
serosal surface of the large intestine except the rectum is
COMPLICATIONS. If the condition is not adequately studded with appendices epiploicae which are small, rounded
managed, the following complications may occur:
collections of fatty tissue covered by peritoneum.
1. Peritonitis. A perforated appendix as occurs in
gangrenous appendicitis may cause localised or generalised Histologically, the wall of large bowel consists of 4 layers as
peritonitis. elsewhere in the alimentary tract—serosa, muscularis,
submucosa and mucosa.
2. Appendix abscess. This is due to rupture of an appendix
giving rise to localised abscess in the right iliac fossa. This The mucosa lacks villi and there is preponderance of CHAPTER 20
abscess may spread to other sites such as between the liver goblet cells over columnar epithelial cells. The lymphoid
and diaphragm (subphrenic abscess), into the pelvis between tissue is less abundant than in the small bowel but lymphoid
the urinary bladder and rectum, and in the females may follicles are seen in the caecum and rectum.
involve uterus and fallopian tubes. The muscularis propria of the large intestine is quite
peculiar—the inner circular muscle layer ensheaths whole
3. Adhesions. Late complications of acute appendicitis are length of the intestine, while the outer longitudinal muscle
fibrous adhesions to the greater omentum, small intestine
and other abdominal structures. layer is concentrated into 3 muscle bands called taenia coli.
The length of outer muscle layer is shorter than the length of
4. Portal pylephlebitis. Spread of infection into mesenteric the intestine and therefore, it forms the sacculations or haustra
veins may produce septic phlebitis and liver abscess. of the large intestine. At the rectosigmoid junction, the three
5. Mucocele. Distension of distal appendix by mucus muscle bands fuse to form a complete covering. The Gastrointestinal Tract
following recovery from an attack of acute appendicitis is The blood supply to the right colon is from the superior
referred to as mucocele. It occurs generally due to proximal mesenteric artery which also supplies blood to the small
obstruction but sometimes may be due to a benign or bowel. The remaining portion of large bowel except the lower
malignant neoplasm in the appendix. An infected mucocele part of rectum receives blood supply from inferior mesenteric
may result in formation of empyema of the appendix. artery. The lower rectum is supplied by haemorrhoidal
branches.
TUMOURS OF APPENDIX The innervation of the large bowel consists of 3 plexuses
of ganglion cells—Auerbach’s or myenteric plexus lying
Tumours of the appendix are quite rare. These include: between the two layers of muscularis, Henle’s plexus lying in
carcinoid tumour (the most common), pseudomyxoma the deep submucosa inner to circular muscle layer, and
peritonei and adenocarcinoma.
Meissner plexus that lies in the superficial mucosa just beneath
CARCINOID TUMOUR. It is already described on page 576. the muscularis mucosae. These are interconnected by non-
Both argentaffin and argyrophil types are encountered, the myelinated nerve fibres.
former being more common. Anal canal, 3-4 cm long tubular structure, begins at the
lower end of the rectum, though is not a part of large bowel,
Grossly, carcinoid tumour of the appendix is mostly but is included here to cover simultaneously lesions
situated near the tip of the organ and appears as a pertaining to this region. It is lined by keratinised or
circumscribed nodule, usually less than 1 cm in diameter, nonkeratinised stratified squamous epithelium. Anal verge
involving the wall but metastases are rare. is the junction between the anal canal and perineal skin, while
Histologically, carcinoid tumour of the appendix pectinate line is the squamo-columnar junction between the
resembles other carcinoids of the midgut. anal canal and the rectum.