This month something about Ascites and a little about dependent edema. But first why write this?
Ascites and edema come up for discussion from time to time with us and I thought to write something about it that might help some of you in reading abstracts or full articles or to ask better questions. Admittedly this is long and wordy and I brushed over several inconvenient truths. Mostly I want to keep my keyboard in good condition in case I should ever have something important to type on it. Anyway should you choose to continue, read it as baseline info …not as a scholarly scientific tome as I’m no scholar. At least it’s acronym free,
Second, some structural considerations.
Ascites is an accumulation of fluid within the normally empty peritoneal sack.The fluid is a transudate, low in protein content, relatively clear and watery. It ‘transudes’ from serum and contains few cells compared to an exudate such as mucous or pus or the thick fluid that exudes from a skin injury or inflammation to form a protective scab. Compared to transudate, exudate is high in protein, cloudy and contains many cells. The abdominal and pelvic cavities are lined with a closed surface, the peritoneum, a tough smooth glistening membrane stretched over the internal surfaces of the muscular walls to form a sort of bag or curtain inside the abdominal cavity.
There are folds and extensions of the peritoneum that partly cover or completely enclose the abdominal organs (viscera) from the outside. Think of it as similar to a finger pushing into a balloon. Like the balloon the peritoneal bag is normally empty except for a film of lubricating mucous so that the folds can slipslide around inside our bellies. To reiterate: the abdominal organs (viscera) are not inside the peritoneal bag. They protrude from the outside. It is normally empty. When the peritoneal cavity does contain fluid the condition is termed Ascites and results in the familiar swollen abdomen, and if there is a lot of fluid the flanks bulge also.
The abdominal and pelvic organs are normally pressed against or bulge into the bag from its outside surfaces in various degrees. Only parts of the stomach, liver, pancreas and kidney surfaces abut the back of the peritoneal sack and are partly covered while the gut is completely enveloped and is fixed or swings from a pedicle of folded peritoneum –the mesentery. The mesentery supports the gut and allows much of it to move on a stalk. It also serves as a conduit for the mesenteric nerves, lymphatics, arteries and veins as they serve the abdominal organs.
The veins from the abdominal organs merge into the larger veins of the portal system. They are the gastric veins from the stomach, the splenic vein from the pancreas and spleen, the superior mesenteric vein from the small intestine and upper (proximal) colon and the inferior mesenteric vein from the lower (distal) colon and rectum.
Unlike other veins in our bodies that connect directly to the heart, the mesenteric vessels first detour thru the liver (portal system) before connecting with the heart. The outgoing mesenteric arteries run parallel with the veins along this two way street. There are some little used standby connections between the portal system veins and the “direct” veins at the lower gullet (esophagus), the belly button (umbilicus), and the anal sphincter (hemorrhoids). They can become important and pose a risk of severe hemorrhage when their fragile and unsupported walls burst under the increased pressure when having to compensate for high portal pressure such as in Budd-Chairi syndrome.
A large broad apron-like mesenteric pedicle, the omentum, hangs down from the transverse colon over the front of the gut. It can be swollen and hugely puffed up with fat. Too many burgers & fries and too many Guiness & Stouts are common etiologic agents.
Next time you are at a bar with some medical hot shots bet them that the peritoneal cavity can connect with the outside world. You’ll win a free beer because it does –in women through the uterine tubes. A convoluted trip, but true.
(these digressions are a good place to break up this mess or delete it)
Third: Now for some functional considerations.
Just as venous blood goes thru the lungs to get reloaded with oxygen and be relieved of various non-essentials or toxins before beginning its arterial journey to serve the rest of the body, the portal blood stops by the liver to make corporal essentials or be relieved of toxins before being collected into the hepatic vein as it heads for the inferior vena cava, the major collecting vein for returning blood to the heart from the lower body.
In addition to solid tumors, a swollen belly can be due to the five F’s (Fat, Fluid, Feces, Flatulence and Fetus), but let’s consider fluid and fat for now. Just as ascitic fluid will make the belly protrude, so will fat (panniculus). In considering ascites, first we need to rule out fat.
If the new health care hasn’t kicked in and you don’t own a personal ultrasound machine yet, you might want to consider two quick and dirty homespun methods to determine if it’s fat or fluid. These are fluid waves and shifting dullness. A palpable and/or visible ‘wave’ will traverse across a potbelly filled with peritoneal fluid or plastered with a thick layer of abdominal fat when either is suddenly disturbed. To feel the wave lay your palm very lightly over your tum to see the wave squint across the surface. Try moving your eyes and the light source into various positions.
We are a courteous caring group, but in this case let’s make waves. If you are sick and your belly is swollen you might wonder if it is due to fluid or fat (ascites or obesity). Slap one side of the belly or flanks smartly and feel and look for the wave on the other side. Is it a fluid wave or a fat wave? Try damping a fat wave by having someone press firmly in the abdominal midline vertically with the heel of her hand. If the wave passes under her hand and is felt on the other side it’s ascites. If the wave doesn’t make it, it’s fat.
If the gut contains gas, thumping on a finger fixed on the belly (percussing) will elicit a tympanic sound over the gaseous areas and a dull or absent sound over non-gaseous areas filled with fluid or solid. As the patient moves into different positions the freely moving ascitic fluid will produce shifting dullness to percussion. Fat
won’t shift altho it shimmies and sways.
After this crisp, cogent and brilliant (who said tedious, stupid and dull?) anatomical and physiological introduction we trudge onward and inward to the troubles and woes and wrong doings (pathology) of the miserable world of clinical ascites.
Ascitic fluid can be squeezed out of the portal system veins by increased hydraulic back pressure due to blockage by a diseased liver or a thrombosed hepatic vein (Budd-Chiari). This is backward failure and the protein content of the fluid will be the same as in the venous blood. With the increased back pressure those standby connections between somatic and portal veins come into play as the blocked portal blood searches for alternate paths back to the heart.
Unfortunately, as with the Gulf oil spill, the standby emergency systems don’t always work right and the walls of the standby veins can become thin and the vessels swollen. They may fail under the increased pressure with bleeding from the lower esophagus, or from piles at the anus and sometimes from the “caput medusa” radiating from the umbilicus.
Dependent edema and ascites can also be due to the arterial circulation not working right with resultant retention of salt and water as in congestive heart failure, liver or kidney disease or sodium overload. This is forward failure and the protein content of the ascitic and edema fluid will be lower than in the blood. As a historical side note; before potent diuretics Southy tubes were used for intractable edema –tiny glass tubes inserted directly through incisions in the skin of the swollen legs to drain off the edema fluid. Usually more fluid drained from the incisions than thru the Southy tubes.
Ascites could be due to malignant peritoneal metastases or primary peritoneal malignancy. If so there will be malignant cells found in the ascitic fluid. Infectious agents such as the tubercle bacillus. fungi, and E. Coli can infect the peritoneum. If so there will be a white cell response and often positive bacterial cultures of the fluid. .
If your home clinical pathology laboratory doesn’t sport a spectrophotometer and flow cytometer or the health care reformation hasn’t provided home magnetic resonance imagery (MRI) yet, there’s a simple examination still available to let you know that your peritoneum is infected or inflamed. It’s called “rebound tenderness” and it’s free. Press firmly on your belly and then release quickly. If your peritoneum is infected or inflamed there will be a jolting rebound pain that will take your breath away and you won’t be likely to try that again.
As far as how you will feel with full blown ascites, I don’t need to tell those of you that suffer it. In addition to the signs and symptoms of the causative agent there will be the usual suspects of any large space occupying lesion in the abdomen –pain or discomfort, poor appetite, quickly being filled up at table, positional difficulties and discomforts and nausea to mention a few of the repeat offenders.
The fluid components of our blood are normally kept safely within the blood vessels by osmotic pressure provided by plasma proteins, mainly albumin. When albumin levels are lowered by malnutrition, kidney or liver disease, cancer or in our case a myeloproliferative neoplasm, the fluid can leak out into the extracellular spaces as ascites or as dependent edema. Pressing with your thumb will displace edema fluid from the area and leave a depression that slowly refills –pitting edema. Lymph edema doesn’t pit very much.
As to treatment of ascites and/or dependemt edema you treat the cause (etiology). There are so many causes that for once I’ll have the grace not to discuss them here. In addition to treating the cause there are various relief measures — diuretics, compression stockings, elastic bandages, physical therapy, elevation, sodium restriction, nutritional supplements and direct assault with a big needle to drain the ascitic fluid (paracentesis).
…and so Dearly Beloved, that’s ascites and edema.
© Dr. Arch M. and MPNforum.com, 2012. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Dr. Arch M. and MPNforum.com with appropriate and specific direction to the original content.