Dr. Ahmed Saleem
FICMS
TUCOM/ 4th Year
THE PERITONEUM, MESENTERY
AND RETROPERITONEAL SPACE
Anatomy and Physiology
The peritoneal cavity is the largest cavity in the body, the surface area of its lining membrane (2 m
2
in an
adult) being nearly equal to that of the skin. The peritoneal membrane is divided into two parts – the
visceral peritoneum surrounding the viscera and the parietal peritoneum lining the other surfaces of the
cavity. In health, only a few milliliters of peritoneal fluid arefound in the peritoneal cavity. The fluid is pale
yellow, somewhat viscid and contains lymphocytes and other leukocytes; it lubricates the viscera, allowing
easy movement and peristalsis. The parietal portion is richly supplied with nerves and, when irritated,
causes severe pain that is accurately localized to the affected area. The visceral peritoneum, in contrast, is
poorly supplied with nerves and its irritation causes pain that is usually poorly localized to the midline.
Functions of the peritoneum
In health
Visceral lubrication
Fluid and particulate absorption
In disease
Pain perception (mainly parietal)
Inflammatory and immune responses
Fibrinolytic activity
Peritonitis
Peritonitis is simply defined as inflammation of the peritoneum and may be localized or generalized. Most
cases of peritonitis are caused by an invasion of the peritoneal cavity by bacteria, so that when the term
‘peritonitis’ is used without qualification, acute bacterial peritonitis is often implied.
Paths to peritoneal infection
Gastrointestinal perforation, e.g. perforated ulcer, appendix, diverticulum
Transmural translocation (no perforation), e.g. pancreatitis, ischemic bowel
Exogenous contamination, e.g. drains, open surgery, trauma
Female genital tract infection, e.g. pelvic inflammatory disease
Hematogenous spread (rare), e.g. septicemia
Localized peritonitis
Anatomical and pathological factors may favour the localizationof peritonitis.
Anatomical
The greater sac of the peritoneum is divided into (1) the subphrenicspaces, (2) the pelvis and (3) the
peritoneal cavity proper. The last is divided into a supracolic and an infracolic compartment by the
transverse colon and transverse mesocolon, which deters the spread of infection from one to the
other.
Pathological
The clinical course is determined in part by the manner inwhich adhesions form around the affected
organ. Inflamed peritoneum loses its glistening appearance and becomes reddened and velvety.
Flakes of fibrin appear and cause loops of intestine to become adherent to one another and to the
parietes. There is an outpouring of serous inflammatory exudate rich in leukocytes and plasma
proteins that soon becomes turbid; if localization occurs, the turbid fluid becomes frank pus.
Peristalsis is retardedin affected bowel and this helps to prevent distribution of the infection. The
greater omentum, by enveloping and becoming adherent to inflamed structures, often forms a
substantial barrier to the spread of infection.
Diffuse (generalized) peritonitis
A number of factors may favour the development of diffuse peritonitis:
Speed of peritoneal contamination is a prime factor.
Stimulation of peristalsis by the ingestion of food or even water hinders localization.
The virulence of the infecting organism may be so great as to render the localization of infection
difficult or impossible.
Young children have a small omentum, which is less effective in localizing infection.
Disruption of localized collections may occur with injudicious handling, e.g. appendix mass or
pericolic abscess.
Deficient natural resistance (‘immune deficiency’).
Clinical features
Localized peritonitis
The initial symptoms and signs of localized peritonitis are those of the underlying condition – usually
visceral inflammation (hence abdominal pain, specific GI symptoms + malaise, anorexia and nausea).
When the peritoneum becomes inflamed, abdominal pain will worsen and, in general, temperature
and pulse rate will rise. The pathognomonic signs are localizedguarding (involuntary abdominal wall
contraction to protect the viscus from the examining hand), a positive ‘release’ sign (rebound
tenderness) and, sometimes, rigidity (involuntary constant contraction of the abdominal wall over
the inflamed parietes).
Diffuse (generalized) peritonitis
Early
Abdominal pain is severe and made worse by moving or breathing. It is first experienced at the site
of the original lesion and spreads outwards from this point. The patient usually lies still. Tenderness
and generalized guarding are found on palpation when the peritonitis affects the anterior abdominal
wall. Infrequent bowel sounds may still be heard for a few hours but they cease with the onset of
paralytic ileus. Pulse and temperature rise in accord with degree of inflammation and infection.
Late
If resolution or localization of generalized peritonitis does not occur, the abdomen will become rigid
(generalized rigidity). Distension is common and bowel sounds are absent. Circulatory failure
ensues, with cold, clammy extremities, sunken eyes, dry tongue, thready (irregular) pulse and drawn
and anxious face. The patient finally lapsesinto unconsciousness. With early diagnosis and adequate
treatment, this condition is rarely seen in modern surgical practice.
Diagnostic aids
Investigations may elucidate a doubtful diagnosis, but theimportance of a careful history and
repeated examination must not be forgotten.
Bedside
Urine dipstix for urinary tract infection
ECG if diagnostic doubt (as to cause of abdominal pain) orcardiac history.
Bloods
Baseline U&E for treatment
Full blood count for white cell count (WCC)
Serum amylase.
Blood group and save serum may be taken as an adjunct toimpending surgery.
Imaging
Erect chest radiograph to demonstrate free subdiaphramatic gas.A supine radiograph of the
abdomen may confirm thepresence of dilated gas-filled loops of bowel (consistent witha
paralytic ileus). In the patientwho is too ill for an ‘erect’ film, a lateral decubitus film canshow
gas beneath the abdominal wall (if CT unavailable).
Multiplanar computed tomography (CT) is increasingly usedto identify the cause of peritonitis
and may also influence management decisions.
Ultrasound scanning has undoubted value in certainsituations such as pelvic peritonitis in
females and localisedright upper quadrant peritonism.
Management of peritonitis
General care of patient
Correction of fluid and electrolyte imbalance
Insertion of nasogastric drainage tube and urinary catheter
Broad-spectrum antibiotic therapy
Analgesia
Vital system support
Operative treatment of cause when appropriate
Remove or divert cause
Peritoneal lavage ± drainage
Complications of peritonitis
Systemic complications
Septic shock
Multiorgan dysfunction syndrome
Abdominal complications
Paralytic ileus
Residual or recurrent abscess/inflammatory mass
Adhesional small bowel obstruction
Intraperitoneal Abscess
Following intraperitoneal sepsis (usually manifest first as local or diffuse peritonitis), abscess development
usually occupies one of a number of specific abdominal or pelvic sites. In general, the symptoms and signs
of a purulent collection may be vague and consist of nothing more than lassitude, anorexia and malaise;
pyrexia (often low-grade), mild tachycardia and localized tenderness. Larger abscesses will give rise to the
picture of swinging pyrexia and pulse and a palpable mass. Blood tests will reveal elevated inflammatory
markers.
Pelvic abscess
The pelvis is the most common site of abscess formation because the vermiform appendix is often pelvic in
position and the Fallopian tubes are also frequent sites of infection. Apelvic abscess can also occur as a
sequel to any case of diffuse peritonitis and is common after anastomotic leakage following colorectal
surgery.The most characteristic symptoms are of pelvic pain, diarrhea and the passage of mucus in the
stools. Rectal examination reveals a bulging of the anterior rectal wall, which, when the abscess is ripe,
becomes softly cystic.
Investigation and management
Left to nature, a proportion of these abscesses burst into the rectum, after which the patient nearly always
recovers rapidly. If this does not occur, the abscess should be drained deliberately. If any uncertainty exists,
the presence of pus should be confirmed by ultrasound or CT scanning. Laparotomy is almost never
necessary and rectal drainage of a pelvic abscess is far preferable to suprapubic drainage, which risks
exposing the general peritoneal cavity to infection.
Subphrenic abscess
The complicated arrangement of the peritoneum results in the formation of four intraperitoneal spaces in
which pus may commonly collect:
Left subphrenic space
The common cause of an abscess here is an operation on the stomach, the tail of the pancreas, the
spleen or the splenic flexure of the colon.
Left subhepatic space/lesser sac
The most common cause of infection here is complicated acute pancreatitis. In practice, a
perforated gastric ulcer rarely causes a collection here because the potential space is obliterated by
adhesions.
Right subphrenic space
Common causes of abscess here are perforating cholecystitis, a perforated duodenal ulcer, a
duodenal cap ‘blow-out’ following gastrectomy and appendicitis.
Right subhepatic space
This lies transversely beneath the right lobe of the liver in Rutherford Morison’s pouch.It is the
deepest space of the four and the most common site of a subphrenic abscess, which usually arises
from appendicitis, cholecystitis, a perforated duodenal ulcer or following upper abdominal surgery.
Clinical features
The symptoms and signs of subphrenic infection are frequently non-specific and it is well to remember the
aphorism, ‘pus somewhere, pus nowhere, pus under the diaphragm’. A common history is that, when some
infective focus in the abdominal cavity has been dealt with, the condition of the patient improves
temporarily but, after an interval of a few days or weeks, symptoms of toxemia reappear. The condition of
the patient steadily, and often rapidly, deteriorates. Sweating, wasting and anorexia are present. There is
sometimes epigastric fullness and pain, orpain in the shoulder on the affected side due to irritation
ofsensory fibers in the phrenic nerve, this being referred along the descending branches of the cervical
plexus. Persistent hiccoughs may be a presenting symptom. A swinging pyrexia is usually present. If the
abscess is anterior, abdominal examination will reveal some tenderness, rigidity or even a palpable swelling.
Sometimes the liver is displaced downwards but more often it is fixed by adhesions.
Investigation and management
Examination of the chest and plain radiograph are important, as in the majority of cases, collapse of the
lung or evidence of basal effusion or even an empyema are evident. The modern management of an
abscess is by radiological diagnosis using ultrasound or CT guidance followed by drainage. The same tube
can be used to instill antibiotic solutions or irrigate theabscess cavity if necessary. Radiolabelled white cell
scanning may occasionally prove helpful when other imaging techniques have failed. Open drainage of an
intraperitoneal collection is thus now uncommon but may be necessary.
Tumors of the Peritoneum
Primary tumors of the peritoneum are rare and in most cases take their origin not from the serous layer but
from some adjacent structures.
Secondary tumors
Carcinomatosis peritonei
This is a common terminal event in many cases of carcinoma of the stomach, colon, ovary or other
abdominal organs and also of the breast and bronchus. The peritoneum, both parietal and visceral, is
studded with secondary growths and the peritoneal cavity becomes filled with clear, straw-colored or
blood-stained ascitic fluid.
Pseudomyxoma peritonei
This rare condition occurs more frequently in women. The abdomen is filled with a yellow jelly, large
quantities of whichare often encysted. The condition is associated with mucinous cystic tumors of the ovary
and appendix. Recent studies suggest that most cases arise from a primary appendiceal tumor with
secondary implantation on to one or both ovaries. It is often painless and there is frequently no impairment
of general health. Pseudomyxoma peritonei does not give rise to extraperitoneal metastases. Although an
abdomen distended with what seems to be fluid that cannot be made to shift should raise the possibility,
the diagnosis is more often suggested by ultrasound and CT scanning or made at operation. At laparotomy,
masses of jelly are scooped out. The appendix, if present, should be excised together with any ovarian
tumor. Unfortunately, recurrence is inevitable, but patients may gain symptomatic benefit from repeated
‘debulking’ surgery. Occasionally, the condition responds to radioactive isotopes or intraperitoneal
chemotherapy.
Peritoneal Adhesions
Pathophysiology
Adhesions are strands of fibrous tissue that form, usually as a result of surgery, between surgically injured
tissues. After injury, there is bleeding and an increase in vascular permeability with extravasation of
fibrinogen-rich fluid from the injured surfaces forming a temporary fibrin matrix. An inflammatory response
ensues with cell migration, release of cytokines, and activation of the coagulation cascade. The activation of
the coagulationsystem results in thrombin formation, which is necessary for theconversion of fibrinogen to
fibrin. In the absence of fibrinolysis, adhesions will form within 5–7 days as the matrix gradually becomes
more organized with collagen secretion by fibroblasts. Fibrinolysis is therefore the key factor in determining
whether an adhesion persists. Of great importance however to the surgeon is the fact that ischemic tissue
loses its ability to break down fibrin and inhibits fibrinolysis in adjacent tissues.
Complications
The most common adhesion-related problem is small bowel obstruction (SBO). Adhesions are implicated as
a major cause of secondary infertility. The relationship of adhesions to chronic abdominal and pelvic pain is
contentious.
The Mesentery
Acute non-specific ileocecal mesenteric adenitis
Non-specific mesenteric adenitis was so named to distinguish it from specific (tuberculous) mesenteric
adenitis. The etiology often remains unknown, although some cases are associated with Yersinia infection
of the ileum. In about 25 per cent of cases, a respiratory infection precedes an attack of non-specific
mesenteric adenitis. This self-limiting disease is never fatal but may be recurrent. Its significance thus
mainly lies in its differential diagnosis with appendicitis in children.
Diagnosis
During childhood, acute non-specific mesenteric adenitis is a common condition. The typical history is one
of short attacks of central abdominal pain lasting from 10 to 30 minutes, commonly associated with
vomiting. The patient seldom looks ill. In more than half of the cases the temperature is elevated.
Abdominal tenderness is poorly localized, and when present, shifting tenderness is a valuable sign for
differentiating the condition from appendicitis. The neck, axillae and groins should be palpated for enlarged
lymph nodes. There is often a leukocytosis of 10 000–12 000 μL or more on the first day of the attack, but
this falls on the second day.
Treatment
When the diagnosis can be made with assurance, bed rest and simple analgesia is the only treatment
necessary. If at a second examination a few hours later, acute appendicitis cannot be excluded, it is safer to
perform either appendectomy or diagnostic laparoscopy.
Mesenteric cysts
Cysts may occur in the mesentery of either the small intestine (60 per cent) or the colon (40 per cent) and
can be classified as:
chylolymphatic.
enterogenous.
urogenital remnant (actually retroperitoneal but project into peritoneum).
dermoid.
Pathology
Chylolymphatic cyst
This is the most common variety, probably arising in congenitally misplaced lymphatic tissue that has no
efferent communicationwith the lymphatic system (most frequently inthe mesentery of the ileum). A
chylolymphatic cyst has a blood supply that is independent from that of the adjacent intestine and, thus,
enucleation is possible without the need for resection of gut.
Enterogenous cysts
These are believed to be derived either from a diverticulum of the mesenteric border of the intestine that
has become sequestrated from the intestinal canal during embryonic life or from a duplication of the
intestine. Both the muscle in the wall of an enteric duplication cyst and the bowel with which it is in contact
have a common blood supply; consequently, removal of the cyst always entails resection of the related
portion of intestine.
Urogenital remnant
A cyst developing in the retroperitoneal space often attains very large dimensions and has first to be
distinguished from a large hydronephrosis. Even after the latter condition has been eliminated by scanning
or urography, a retroperitoneal cyst can seldom be distinguished with certainty from a retroperitoneal
tumor until displayed at operation. Many of these cysts are believed to be derived from a remnant of the
Wolffian duct, in which case they are filled with clear fluid.
Presentation
The most common presentation is of a painless abdominal swelling with characteristic physical
signs: there is a fluctuant swelling near the umbilicus, the swelling moves freely in a plane at right
angles to the attachment of the mesentery (Tillaux’s sign), there is a zone of resonance around the
cyst.
Other presentations:
recurrent attacks of abdominalpain with or without vomiting (pain resulting from
recurringtemporary impaction of a food bolus in a segment ofbowel narrowed by the cyst or
possibly from torsion of themesentery) and acute abdominal catastrophe; due totorsion of
that portion of the mesentery containing thecyst.
rupture of the cyst, often as a result of a comparativelytrivial accident.
hemorrhage into the cyst.
Infection.
The Retroperitoneal Space
Retroperitoneal chronic inflammation/fibrosis
This is a relatively rare diagnosis characterized by the development of a flat grey/white plaque of tissue
which is found first in the low lumbar region but then spreads laterally and upwards to encase the common
iliac vessels, ureters and aorta. Its etiology is obscure in most cases (idiopathic) being allied to other
fibromatoses (e.g. Dupuytren’s contracture). In other patients the cause is known:
Benign
Idiopathic (Ormond’s disease)
Chronic inflammation
Extravasation of urine
Retroperitoneal irritation by leakage of blood or intestinalcontent
Aortic aneurysm (inflammatory type)
Trauma
Drugs (chemotherapeutic agents and previouslymethysergide)
Malignant
Lymphoma
Carcinoid tumors
Secondary deposits (especially from carcinoma of stomach,colon, breast and prostate)
The clinical presentation may be one of ill-defined chronic backache or may occur as a result of compromise
to involved structures, e.g. lower limb or scrotal edema secondary to venous occlusion, or chronic renal
failure secondary to ureteric obstruction. Treatment will be directed to the cause, to the modification of
disease activity when appropriate, e.g. immune suppression with steroids and restoration of flow in
affected structures, e.g. ureteric stenting.
Retroperitoneal tumors
Although swellings in the retroperitoneum may include abscess, hematoma, cysts and spread of malignancy
from retroperitoneal organs (kidney, ureter, adrenal), the term retroperitoneal tumor is usually confined to
primary tumors arising in other tissues in this region, e.g. muscles, fat, lymph nodes and nerves. The
management of such tumors is now frequently by referral to a specialist center and this should be done
beforebiopsy which may compromise subsequent surgical cure.