Physiology of Defecation

Physiology of Defecation

• Defecation is the expulsion of feces from the rectum which has both involuntary and voluntary components
• When feces enter the rectum, distention & pressure create sensory impulses
• These impulses begin reflex actions in the internal anal sphincter, sigmoid colon, and rectum muscles
• The sphincter relaxes and muscles contract, which moves feces to the anal canal
• The external anal sphincter has voluntary control that must relax for rectal evacuation to occur
• Contraction of abdominal muscles and forceful expiration with a closed glottis (Valsalva Maneuver) can aid voluntary defecation
• If ignored, the defecation reflex dissipates, potentially resulting in constipation due to desensitization of local stimulation
• Fecal passage through the large intestine takes 24-48 hours
• Feces include undigested food, digestive secretions (gastric, intestinal, pancreatic, & liver), water, and microorganisms
• Rapid movement of feces results in liquid stool as less water is absorbed
• Delay causes excessive water absorption leading to hard, dry stool

Normal Stool Characteristics

• Color is yellow or golden brown from stercobilin, a bile pigment derivative
• Odor is aromatic, produced by indole and skatole which are byproducts of fermentation and putrefaction
• Amount depends on food intake

Alterations in Stool Characteristics

• Alcoholic stool is gray, pale, or clay-colored due to biliary obstruction
• Hematochezia marks the passage of stool with bright red blood, sourced from lower GI bleeding
• Melena involves passage of black, tarry stool due to upper GI bleeding
• Steatorrhea presents as greasy, bulky, foul-smelling stool from hepatobiliary-pancreatic obstruction/disorders

Common Fecal Elimination Problems & Solutions

• Constipation is the passage of small, dry, hard stools or absence of stool
• To relieve it, adequate fluid and a high-fiber diet are needed, including fruits, nuts, vegetables, and whole grains in meals
• Avoid foods low in fiber such as fish, milk, meat, and eggs
• Establish a defecation pattern, respond to urges without delay, minimize stress, engage in activity and exercise, and use laxatives when ordered
• Excessive laxative use should be avoided, as it can inhibit natural reflexes and cause rebound constipation

Types of Laxatives

• Chemical irritants stimulate peristalsis by irritating the intestinal wall, such as Dulcolax (bisocodyl), castor oil, and Senokot (senna)
• Stool lubricants, like mineral oil, lubricate feces to ease expulsion
• Stool softeners soften feces to facilitate expulsion, for example, Colace
• Bulk-formers, such as Metamucil increase fecal bulk, raising mechanical pressure and intestinal distention to enhance peristalsis
• Osmotic agents draw fluids from intestinal capillaries into the stool, such as milk of magnesia

Fecal Impactions

• Fecal impaction involves hardened, putty-like feces in the rectum
• Asses for liquid fecal seepage, palpable hard fecal masses, painful nonproductive defecation urges, anorexia, abdominal distention, nausea and vomiting
• Manual extraction, increased fluids, sufficient diet bulk, and activity can relieve impaction

Diarrhea

• Diarrhea is the passage of liquid feces with increased frequency
• Measures involve replacing fluid-electrolyte loss, perineal care, rest, and small amounts of low-fiber foods
• The BRAT diet (banana, rice, applesauce, and toast) is recommended, avoiding very hot or cold fluids
• Consuming potassium-rich food and fluids (banana and Gatorade) can replenish electrolytes
• Demulcents protect the bowel by mechanically coating irritated areas
• Adsorbents absorb gas or toxic substances from the bowel
• Astringents shrink swollen or inflamed tissues
• Antidiarrheals should not be administered at diarrhea's onset, given that it is the body's protective response to remove bacteria & toxins

Flatulence

• Flatulence is the presence of excessive intestinal gas, also known as tympanites
• Common causes include constipation, medications like codeine and barbiturates, anxiety, gas-forming foods (like chayote and cabbage), and abdominal surgery
• To relieve, avoid gas-forming foods, intake warm fluids, early ambulation, adequate activity and exercise
• Limit gum chewing, carbonated drinks, and use of straws
• When ordered, rectal tube insertion, carminative enemas, and cholinergics can be administered

Enemas

• An enema introduces solution into the rectum and sigmoid colon

Enema Purposes

• Relieve constipation and flatulence
• Facilitate medication administration
• Lower body temperature

Enema Restrictions

• Active labor
• Vaginal bleeding
• Ruptured amniotic sac
• Abnormal fetal position and presentation
• Unengaged fetus
• Risk of cord prolapse stemming from premature labor
• Abnormal fetal heart rate pattern

Common Uses for Enemas

• Temporary constipation relief
• Removal of impacted feces
• Bowel emptying before diagnostics, surgery, or childbirth; bowel training

Enema Reminders

• Discourage overuse to maintain regularity
• Do not address the underlying cause of constipation

Enema Types

• Cleansing enemas stimulate peristalsis through colon/rectum irritation or intestinal distention with fluid volume
• High enemas cleanse more of the colon using a large amount of solution
• Low enemas target only the rectum & sigmoid colon

Cleansing Enema Types

• Tap water is hypotonic and exerts lower osmotic pressure, but it should not be repeated
• Normal saline is the safest due to its equal osmotic pressure
• Hypertonic solutions draw fluid via high osmotic pressure, commonly using a commercially available Fleet enema
• Soap suds may irritate intestines, use pure castile soap
• Carminative enemas expel flatus by relieving gaseous distention with 60-180ml fluid
• Retention enemas introduce oil to soften feces for 1-3 hours easing passage

Return-Flow Enema

• Return-flow enemas (Harris flush/colonic irrigation) expel flatus
• Involves introducing 100-200 ml of fluid and then removing it to stimulate peristalsis; repeat the inflow-outflow process 5-6 times

Steps for Return Flow Enema

• Wash hands, assess client understanding, apply gloves
• Position client in left lateral with absorbent pad underneath
• Warm the solution, pour, prime tubing, and clamp
• Lubricate the rectal tube (unless prelubricated)
• Hold the enema container level with, and insert the rectal tube cm while the client inhales deeply
• Raise the solution container and infuse approximately 200cc of solution
• Clamp, lower container 12-18 inches below the client to observe return of air bubbles and feces, repeat until only fluid returns
• Complete the procedure
• Repeat until no further flatus is seen or if institutional guidelines are met
• Clean the anus, assist in emptying the rectum, and clean perineal area

Medicated Enemas

• Medicated enemas contain drugs to reduce microorganisms and bacteria
• Sodium Polystyrene Sulfonate aims to treat high serum potassium levels by exchanging potassium ions for sodium
• Another medicated enema is neomycin solution
• Antibiotics such as neomycin can reduce bacteria prior to a bowel surgery

Sedative Enemas

• Sedative enemas induce sleep, calmness, and decreased anxiety

Non-Retention Enemas

• Non-retention enemas use tap water, soap suds, normal saline, or hypertonic solutions
• They are administered with the solution container 18 inches above the rectum
• Are administered at 115-125 degrees F
• And should be held for 5-10 mins

Retention Enemas

• Retention enemas include carminative and oil retention solutions
• They are given with the solution container 12 inches above the rectum
• The temperature of the solution should be 105 to 110 degrees F

Administering an Enema - Assessment

• Identify the category of the enema and its purpose
• Assess the client’s physical and mental condition

Administering an Enema - Outcomes

• A rectum clear of feces and flatus is expected
• Client discomfort should be minimized

Interventions for Large Volume Cleansing Enemas

• Wash hands, provide privacy, and explain the procedure to the client
• Apply gloves, and prepare the equipment
• In the left lateral position, place an absorbent pad
• Use 115-125 degrees F in a non retention enema
• Prime tubing, lubricate (if not pre-lubricated) 7-10 cm, and gently insert the rectal tube while client inhales deeply
• Elevate the container to the appropriate height (12-18 inches) at the proper temperature
• Avoid over administration of fluids to prevent complications
• Administer fluids gradually and if the client cannot tolerate fluids slow or stop the administration
• Remove and dispose rectal tube appropriately, and clean any residue from the anus
• Maintain left lateral position per protocol
• Assist patient once they feel the need to go
• Document the results after removing gloves

Small Volume Pre-Packed Enema Administration

• Remove the pre-packed enema from packaging and warm it before use
• Apply gloves and place an absorbent pad, and assist the patient into left lateral position
• Take the protective cap from the nozzle and lubricate if need
• Squeeze container
• Remove any air and prime nozzle
• Insert enema nozzle and squeeze container
• Remove the nozzle from the anus