Urethral Obstruction / Urinary Blockage

Urethral obstruction, also known as urinary blockage, is a life-threatening emergency condition in guinea pigs where the flow of urine from the bladder is partially or completely blocked. This obstruction prevents normal urination and causes rapid accumulation of urine in the bladder, leading to severe pain, bladder distension, and potential rupture if not treated immediately. Understanding urethral obstruction is critical for guinea pig owners because this condition can progress from apparent health to life-threatening crisis within hours, and delays in seeking treatment dramatically worsen outcomes.

Urethral obstruction occurs more frequently in male guinea pigs than females due to their longer, narrower urethras, which are more susceptible to blockage by stones, sludge, or urethral plugs. However, female guinea pigs can also experience blockages, particularly from larger stones lodged at the bladder neck or urethra. The condition may develop suddenly when a stone shifts into an obstructing position, or gradually worsen as sludge accumulates and increasingly impedes urine flow. Guinea pigs with a history of urinary tract problems, particularly bladder stones or sludge, are at significantly elevated risk.

The impact of urethral obstruction on a guinea pig's health is severe and rapidly progressive. Complete obstruction causes excruciating pain as the bladder distends and pressure builds throughout the urinary system. Toxins normally eliminated in urine accumulate in the bloodstream, leading to uremia with its multisystemic effects. Electrolyte imbalances, particularly dangerous elevations in potassium, can cause fatal cardiac arrhythmias. Kidney damage occurs from back-pressure when urine cannot drain, and this damage may become permanent within twenty-four to forty-eight hours. Without treatment, urethral obstruction is fatal.

Urethral obstruction is treatable when recognized and addressed promptly, but outcomes depend heavily on how quickly treatment is initiated. Emergency treatment to relieve the obstruction and stabilize the guinea pig must occur as soon as possible, ideally within hours of symptom onset. Even with successful relief of the acute obstruction, underlying causes must be addressed to prevent recurrence, and some guinea pigs suffer permanent kidney damage despite treatment. Guinea pig owners must recognize the signs of urinary obstruction and understand that this is a true emergency requiring immediate veterinary care at any time of day or night.

The primary causes of urethral obstruction in guinea pigs involve physical blockage of the urethra by stones, sludge, plugs, or other obstructing materials. Urinary stones, also called calculi or uroliths, are the most common cause of complete obstruction. These stones form in the bladder from mineral crystallization and can become lodged in the urethra when they attempt to pass during urination. In guinea pigs, most urinary stones are composed of calcium carbonate or calcium oxalate, reflecting their unique calcium metabolism. Bladder sludge, a thick accumulation of calcium crystite suspended in mucus, can cause partial or complete obstruction as it accumulates and blocks urine flow.

Genetic and hereditary factors may predispose some guinea pigs to urinary stone formation and subsequent obstruction risk. While specific genes have not been identified, certain guinea pigs appear more prone to forming stones despite appropriate husbandry, suggesting hereditary susceptibility. Male guinea pigs have an anatomical predisposition due to their long, narrow, curved urethra with a small external opening, making them more likely to experience obstruction than females. Some breeding lines may have tendencies toward hypercalciuria, excessive calcium excretion in urine, which promotes stone formation. Congenital urinary tract abnormalities, though uncommon, can create areas where stones or debris accumulate.

Environmental factors significantly contribute to urinary stone formation and obstruction risk. Inadequate water intake from poor water bottle function, unappealing water, or insufficient access leads to concentrated urine that promotes crystallization. Diet high in calcium, particularly from excessive alfalfa hay, calcium-rich vegetables, or inappropriate supplements, increases urinary calcium levels. Insufficient hay consumption reduces fiber intake and may alter urinary pH in ways promoting stone formation. Sedentary lifestyle in small enclosures reduces natural movement that helps keep urinary sediment suspended. Vitamin C deficiency affects tissue health throughout the urinary tract and may contribute to stone formation.

Risk factors for urethral obstruction include any factor that promotes stone formation or affects urinary tract function. Male sex is the most significant anatomical risk factor due to urethral anatomy. Age plays a role, with middle-aged to senior guinea pigs being at higher risk as cumulative stone formation occurs. History of previous urinary problems, including stones, sludge, or infections, substantially increases future obstruction risk. Obesity is associated with increased urinary problems and overall health compromise. Chronic dehydration from any cause promotes stone formation. Recurrent urinary tract infections can create a matrix that promotes stone nucleation and growth.

The mechanism of urethral obstruction involves physical blockage of urine flow with rapidly escalating consequences. When a stone, plug, or accumulation of sludge lodges in the urethra, urine can no longer pass from the bladder. The bladder continues to fill from ongoing kidney function, becoming progressively distended and painful. Pressure builds throughout the urinary system, transmitting back to the kidneys and causing hydronephrosis, distension of the kidney collecting system. Continued obstruction causes kidney tissue damage from back-pressure. Toxins including urea, creatinine, and potassium accumulate in the bloodstream, causing systemic toxicity. Severe bladder distension can lead to bladder wall necrosis or rupture. Hyperkalemia, elevated blood potassium, can cause fatal cardiac arrhythmias. This cascade of events occurs over hours to days, making rapid recognition and treatment essential.

Early warning signs of developing urethral obstruction may be subtle initially but typically progress rapidly to obvious distress. Frequent visits to urination spots with small or no urine production indicate developing obstruction. Straining posture, with the guinea pig hunching and appearing to push without results, is an important early sign. Vocalizing during urination attempts, including squeaking or crying, indicates pain. Small amounts of blood in urine or on bedding may appear as stones or sludge irritate the urinary tract lining. Mild lethargy or reduced activity may develop as discomfort begins affecting the guinea pig's behavior.

Common symptoms of established urethral obstruction become unmistakable as the condition progresses. Repeated, unproductive straining to urinate, often with the guinea pig adopting a stretched-out posture and visibly pushing, is characteristic. Complete absence of urine in the cage despite normal or increased drinking raises immediate concern. Wet fur around the genital area without actual urination suggests dribbling from overflow rather than normal voiding. Pronounced lethargy and reluctance to move develop as pain and toxin accumulation worsen. Loss of appetite occurs as the guinea pig feels increasingly unwell. Abdominal enlargement may become visible as the bladder distends.

Behavioral changes in guinea pigs with urethral obstruction reflect severe pain and distress. Affected guinea pigs may become unusually still or conversely quite restless, unable to find a comfortable position. Teeth grinding, a sign of pain in guinea pigs, may be audible. Aggressive or defensive behavior when touched, particularly around the abdomen, indicates pain. Complete withdrawal from interaction with cage mates and humans reflects severe discomfort. Hiding behavior increases as the guinea pig instinctively seeks isolation when severely ill. Normal vocalizations cease as the guinea pig focuses entirely on its distress.

Physical signs of urethral obstruction provide diagnostic clues during examination. A markedly distended, firm bladder may be palpable or even visible as abdominal enlargement. The genital area may appear swollen or irritated from straining attempts. Dehydration develops despite water intake, manifesting as sunken eyes and decreased skin elasticity. Hypothermia, abnormally low body temperature, occurs as circulation and metabolism become compromised. Pale mucous membranes may indicate shock or developing anemia. In some cases, a stone may be visible or palpable at the urethral opening or along the penile urethra in males.

Symptom progression in urethral obstruction follows a rapidly deteriorating course. What begins as frequent straining progresses over hours to complete inability to urinate with obvious distress. Pain and lethargy worsen as bladder distension increases and toxins accumulate. Gastrointestinal function shuts down secondary to pain and metabolic derangement, leading to dangerous stasis. Cardiovascular effects from electrolyte imbalances may cause weakness, collapse, or sudden death. Neurological signs including confusion or unresponsiveness develop with advancing uremia. Without intervention, death typically occurs within twenty-four to seventy-two hours of complete obstruction.

Emergency symptoms requiring immediate veterinary intervention include any suspicion of inability to urinate, which should be treated as emergency until proven otherwise. Complete absence of urination for six or more hours with straining attempts is a critical emergency. Vocalizing in pain with urination attempts indicates significant distress. Abdominal distension or a palpable, firm bladder confirms dangerous accumulation. Collapse, extreme weakness, or unresponsiveness suggests advanced crisis with potential cardiac effects from hyperkalemia. Any guinea pig showing these symptoms requires immediate transport to an exotic veterinarian or emergency facility, regardless of time of day. This is one of the few true emergencies where hours matter for survival.

Initial examination by an exotic veterinarian experienced with guinea pigs in an emergency setting begins with rapid assessment of urinary status. The veterinarian gathers brief history about symptoms, duration, and any previous urinary problems while simultaneously evaluating the guinea pig. Palpation of the abdomen assesses bladder size, with a severely distended, firm bladder confirming obstruction. Examination of the genital area and external urethra may reveal a stone at the urethral opening, particularly in males. Vital signs assessment identifies shock, dehydration, or hypothermia requiring immediate supportive intervention. The severity of the guinea pig's condition determines whether diagnostic testing proceeds or emergency relief of obstruction takes priority.

Diagnostic tests for urethral obstruction include imaging to locate stones and bloodwork to assess systemic effects. Radiographs of the abdomen and pelvis are the primary diagnostic tool, as most guinea pig urinary stones are radiopaque and visible on x-rays. Stone location, size, and number can be determined, guiding treatment planning. Ultrasound may provide additional information about bladder wall condition, kidney involvement, and detection of radiolucent stones that might not appear on x-rays. Blood chemistry panels evaluate kidney function through blood urea nitrogen and creatinine levels, and critically assess potassium levels, as hyperkalemia is the most immediately life-threatening consequence of obstruction. Complete blood count provides baseline values and may reveal infection or anemia.

Differential diagnosis involves distinguishing complete urethral obstruction from other causes of straining and urinary symptoms. Severe urinary tract infection can cause straining, pain, and blood in urine but typically allows some urine passage. Bladder masses or polyps may cause urinary symptoms without complete obstruction. Intestinal impaction or constipation can cause straining that might be confused with urinary straining. Reproductive tract problems in both males and females can cause similar postures and discomfort. Pain from other abdominal conditions may cause hunched posture resembling urinary straining. Physical examination, imaging, and inability to express urine from the bladder help confirm true urethral obstruction.

Confirmation and severity assessment guides emergency treatment decisions. Confirmation of obstruction comes from identifying a distended bladder that cannot be expressed, combined with imaging showing stone location. Assessment of systemic status through bloodwork identifies life-threatening hyperkalemia requiring specific intervention. Kidney function assessment indicates the degree of damage that may have already occurred. Evaluation of overall stability determines whether the guinea pig can safely undergo anesthesia for obstruction relief or requires stabilization first. The location and nature of the obstruction, whether stone, plug, or sludge, guides the choice of intervention technique.

Emergency and immediate treatment of urethral obstruction focuses on relieving the blockage and stabilizing the guinea pig's critical status. Initial stabilization may include intravenous or subcutaneous fluids to address dehydration and begin toxin dilution. Pain management with guinea pig-safe analgesics such as meloxicam is essential. If severe hyperkalemia is detected or suspected, specific treatment with calcium gluconate and other interventions may be necessary to protect the heart before anesthesia. Warming support addresses hypothermia common in severely affected guinea pigs. Once minimally stabilized, relief of the obstruction is the priority because the bladder cannot remain distended without risking rupture and death.

Medical management to relieve obstruction involves attempts to clear the blockage without surgery when possible. Gentle massage and manipulation of the urethral area may dislodge stones at the external opening in males. Retrograde flushing, where saline is gently infused into the urethra under sedation or anesthesia, may push stones back into the bladder where they can be removed surgically under controlled conditions. In female guinea pigs, the shorter, wider urethra sometimes allows passage of smaller stones with hydration and gentle manipulation. Cystocentesis, using a needle to drain urine directly from the bladder through the abdominal wall, can provide temporary relief of pressure while preparing for definitive treatment but does not address the underlying obstruction.

Surgical options are frequently necessary for complete relief of urethral obstruction. Cystotomy, surgical opening of the bladder, allows removal of stones from the bladder and is often combined with flushing stones back from the urethra into the bladder for removal. Urethrotomy, incision into the urethra, may be required for stones firmly lodged in the urethra that cannot be dislodged by flushing. Perineal urethrostomy, creating a permanent new urethral opening, may be considered in male guinea pigs with recurrent obstruction to bypass the narrowest portion of the urethra. All surgical procedures carry anesthetic risk, particularly in compromised patients, but are often the only option for restoring urinary function.

Supportive care during and following treatment addresses the systemic effects of obstruction and promotes recovery. Continued fluid therapy helps clear accumulated toxins and maintains hydration during recovery. Syringe feeding with critical care formulas prevents gastrointestinal stasis, which guinea pigs cannot tolerate. Vitamin C supplementation supports healing and overall health. Pain management continues throughout recovery to maintain comfort and encourage eating. Bladder support medications may be prescribed to promote bladder function and reduce spasm. Antibiotics safe for guinea pigs, such as enrofloxacin or trimethoprim-sulfa, may be prescribed to prevent or treat infection, but penicillin-type antibiotics must never be used as they are potentially fatal to guinea pigs.

Alternative and complementary treatments may support recovery but cannot replace emergency obstruction relief. Herbal supplements promoted for urinary health should only be used with veterinary guidance during the recovery period. Ensuring optimal hydration through high-moisture foods and encouraging water intake supports urinary tract flushing. Environmental modifications to reduce stress support overall recovery. Dietary modifications to reduce stone recurrence risk begin during the recovery period. No alternative treatment can address an acute obstruction, which requires immediate medical or surgical intervention.

Treatment decision factors that influence approach include the stability of the guinea pig, which determines whether immediate surgery or stabilization first is appropriate. The location of obstruction guides the technique for relief, with stones at different locations requiring different approaches. Stone composition, if known from previous episodes, influences long-term prevention strategies. The guinea pig's overall health, age, and concurrent conditions affect surgical risk and prognosis. Owner factors including ability to provide intensive post-operative care and afford treatment influence decision-making. In cases where severe kidney damage has already occurred or the guinea pig is in extreme decline, quality of life considerations may influence whether aggressive treatment is pursued.

Recovery timeline for guinea pigs following urethral obstruction treatment varies based on the duration of obstruction, degree of systemic compromise, and extent of intervention required. Guinea pigs treated early, before significant toxin accumulation or kidney damage, may recover relatively quickly over one to two weeks. Those who experienced prolonged obstruction with systemic toxicity require more extended recovery periods of several weeks. Post-surgical patients need healing time for incisions in addition to recovery from the obstruction itself. Some guinea pigs suffer permanent kidney damage despite successful obstruction relief, requiring ongoing management.

Post-treatment care following obstruction relief requires intensive attention to multiple aspects of the guinea pig's health. Continued fluid therapy, often subcutaneously at home, helps clear residual toxins and supports kidney recovery. Syringe feeding with critical care formulas continues until appetite fully returns, which may take several days. Pain management with prescribed medications maintains comfort and encourages eating and activity. Monitoring urination carefully confirms that obstruction has been fully relieved and has not recurred. Restricting activity may be necessary following surgical procedures to allow incision healing. Follow-up veterinary visits with repeat bloodwork assess kidney function recovery and identify any complications.

Prognosis factors influencing outcome include the duration of obstruction before treatment, which correlates strongly with outcome. Guinea pigs treated within hours of obstruction generally have good prognoses, while those obstructed for more than twenty-four hours face worse outcomes. The degree of kidney damage, assessed through bloodwork, significantly affects long-term prognosis. Successful removal of all stones without surgical complications predicts better outcomes. The guinea pig's age and overall health status prior to obstruction influence recovery capacity. Development of post-treatment complications such as infection, recurrent obstruction, or gastrointestinal stasis worsens prognosis.

Long-term outlook for guinea pigs surviving urethral obstruction depends heavily on prevention of recurrence and any permanent damage sustained. Guinea pigs with single episode due to correctable causes and no lasting kidney damage may have excellent long-term prognosis with preventive management. Those with recurrent stone formation face ongoing risk of future obstruction despite dietary and medical prevention. Permanent kidney damage from the obstruction episode may require lifelong management with fluid therapy and dietary modification. Understanding that urethral obstruction can recur despite best efforts, and maintaining vigilance for early symptoms, is essential for these high-risk guinea pigs. Regular veterinary monitoring with periodic imaging helps detect new stone formation before obstruction occurs.

Primary prevention of urethral obstruction focuses on preventing the formation of urinary stones and sludge that cause blockages. Ensuring constant access to fresh, clean water and encouraging drinking maintains dilute urine that reduces crystallization risk. Daily vitamin C supplementation of twenty-five to fifty milligrams supports tissue health and may help prevent stone formation. Providing unlimited timothy hay rather than calcium-rich alfalfa hay after guinea pigs mature past six months to one year helps control calcium intake. Avoiding calcium supplements and limiting high-calcium vegetables in guinea pigs prone to urinary problems reduces urinary calcium levels.

Environmental prevention addresses factors that influence urinary health and stone formation risk. Providing appropriately sized housing with opportunity for exercise promotes natural movement that helps keep urinary sediment suspended. Maintaining clean, dry bedding and sanitary conditions reduces urinary tract infection risk, which can contribute to stone formation. Ensuring water bottles function properly with daily checking prevents inadvertent dehydration. Positioning water and food to encourage movement and activity throughout the day supports overall health. Reducing stress through appropriate social grouping and environmental enrichment supports immune function and overall health.

Dietary prevention is particularly important for guinea pigs at risk of urinary stones and obstruction. Timothy hay should comprise the majority of the diet, with unlimited access throughout the day. Fresh vegetables should be offered daily, emphasizing vitamin C-rich options like bell peppers while limiting high-calcium vegetables such as kale and spinach. High-moisture vegetables contribute to hydration and urinary dilution. Avoiding alfalfa hay in adult guinea pigs reduces calcium intake significantly. Commercial pellets should be fed in limited quantities, with timothy-based pellets preferred over alfalfa-based formulations. Treats and processed foods should be minimized or eliminated.

Health maintenance through regular veterinary care enables detection of developing urinary problems before obstruction occurs. Regular wellness examinations by an exotic veterinarian allow early detection of bladder sludge or stone formation through palpation and history. Periodic urinalysis can detect abnormalities suggesting stone formation risk. Abdominal radiographs in guinea pigs with history of urinary problems or symptoms can identify stones while small and more easily managed. Weight management through appropriate diet and exercise reduces overall health risks including urinary problems. Prompt treatment of urinary tract infections prevents complications that could contribute to stone formation.

Early intervention strategies for guinea pigs showing signs of urinary problems prevent progression to obstruction. Seeking veterinary attention at the first sign of urinary symptoms, including frequent urination, straining, or blood in urine, enables early treatment. Beginning increased hydration through water supplementation, high-moisture vegetables, and possibly subcutaneous fluids when early stones or sludge are detected may prevent progression. Dietary modification to reduce calcium intake should begin immediately when urinary problems are identified. Medical management of early stone formation may prevent growth to sizes that cause obstruction. Understanding that urinary symptoms in guinea pigs should always be taken seriously, as obstruction can develop rapidly, encourages appropriate urgency in seeking care.

Daily management and care adjustments for guinea pigs who have experienced urethral obstruction focus on preventing recurrence while maintaining quality of life. Monitoring urination patterns carefully, including frequency, volume, straining, and urine appearance, allows early detection of developing problems. Ensuring constant access to fresh water and encouraging drinking through multiple water sources, fresh vegetables, and possibly adding small amounts of unsweetened juice to water helps maintain dilute urine. Administering any prescribed medications, including urinary acidifiers or other prevention medications, consistently supports prevention. Weighing the guinea pig regularly and monitoring food intake helps detect subtle changes that might indicate developing health issues.

Home environment optimization supports urinary health and overall well-being for at-risk guinea pigs. Providing ample space for exercise and activity promotes natural movement that helps prevent sediment accumulation in the bladder. Ensuring bedding is always clean and dry prevents urinary tract infections that can contribute to stone formation. Maintaining appropriate environmental temperature prevents dehydration from excessive heat. Positioning multiple water sources throughout the enclosure encourages frequent drinking. Using shallow water dishes in addition to bottles may encourage increased water consumption in some guinea pigs.

Quality of life maintenance requires balancing preventive measures with the guinea pig's enjoyment and natural behaviors. Providing a varied diet within the restrictions necessary for urinary health keeps mealtimes interesting and encourages eating. Offering appropriate enrichment and social interaction supports psychological well-being. Allowing normal activities while remaining vigilant for signs of urinary problems permits the guinea pig to enjoy life while staying protected. Working with the veterinarian to find the least restrictive effective prevention strategy minimizes impact on the guinea pig's quality of life.

Monitoring and ongoing care involves vigilant observation and regular veterinary assessment for guinea pigs at risk of recurrent obstruction. Keeping a daily log of urination patterns, water intake, food consumption, and any behavioral changes provides valuable information for detecting early problems. Attending scheduled follow-up veterinary appointments for physical examination and periodic imaging allows detection of new stone formation before obstruction occurs. Communicating promptly with the veterinarian about any changes in urination, behavior, or appetite enables timely intervention. Understanding the symptoms of obstruction and having a plan for emergency care, including knowing the nearest emergency exotic veterinary facility, prepares owners to respond quickly if obstruction recurs.

Caregiver support and resources help owners manage the ongoing vigilance required for guinea pigs at risk of obstruction. Connecting with guinea pig communities provides emotional support and practical advice from owners who have managed similar situations. Maintaining open communication with the veterinary team ensures caregivers understand prevention strategies and warning signs. Developing routines for monitoring and preventive care helps ensure consistency without excessive anxiety. Understanding that despite best efforts, some guinea pigs will experience recurrence, and that this is not a failure of care, helps owners cope with the challenges of managing this condition.

High-risk breeds for urethral obstruction are not definitively established because obstruction relates to stone formation and anatomy rather than breed-specific factors, but certain characteristics elevate risk. Male guinea pigs of any breed are at significantly higher risk than females due to their long, narrow, curved urethra that is susceptible to blockage. Guinea pigs of any breed with history of bladder stones, sludge, or urinary tract infections face elevated obstruction risk. Senior guinea pigs may be at higher risk due to accumulated stone formation over time. Guinea pigs from breeding lines with known urinary problems may have hereditary susceptibility to stone formation.

Moderate-risk breeds and general considerations apply across the guinea pig population. All guinea pig breeds are susceptible to urinary stone formation and potential obstruction, as this relates to species-specific calcium metabolism rather than breed characteristics. Short-coated breeds may have no different risk than long-coated breeds for urinary problems specifically. Guinea pigs fed inappropriate diets high in calcium, regardless of breed, face elevated stone formation risk. Obese guinea pigs of any breed may have higher urinary problem risk. Those with limited exercise opportunity or water intake have increased risk regardless of breed.

Screening recommendations for breeders and owners focus on early detection and prevention rather than breed-specific concerns. Breeders should maintain health records including any urinary problems in their guinea pigs and breeding lines. Guinea pigs with recurrent urinary stones should generally not be bred, as susceptibility may have genetic components. New owners should be educated about urinary health, appropriate diet, and warning signs of urinary problems. Regular veterinary examinations including attention to urinary health should be encouraged for all guinea pigs. Male guinea pigs and those with any urinary history should receive heightened monitoring and preventive care.

Commonly co-occurring conditions with urethral obstruction include other urinary tract problems that share underlying causes. Bladder stones are the primary cause of most obstructions and may recur even after successful treatment. Bladder sludge, accumulation of calcium crystite, often accompanies stone disease and can cause partial obstruction or contribute to complete blockage. Urinary tract infections may precede, accompany, or follow obstruction, requiring antibiotic treatment. Uremia develops rapidly with complete obstruction as toxins accumulate, affecting multiple organ systems. Kidney damage from back-pressure during obstruction may persist as chronic kidney disease requiring ongoing management.

Conditions with similar symptoms that must be differentiated from urethral obstruction include other causes of straining and urinary difficulty. Severe cystitis or bladder infection causes pain and straining but usually allows some urination. Bladder tumors or polyps can cause urinary symptoms without complete obstruction. Intestinal impaction or constipation may cause straining postures that resemble urinary straining. Reproductive tract problems including impacted boar glands in males or reproductive masses in females can cause similar symptoms. Pain from other abdominal conditions may cause hunched postures. Careful examination, imaging, and assessment of bladder status distinguish these conditions from true urethral obstruction.

Potential complications of urethral obstruction encompass the serious problems that may develop during the obstruction or following treatment. Uremia with its multisystemic toxicity develops rapidly with complete obstruction and can cause death if not treated. Bladder rupture can occur with severe distension, causing urine leakage into the abdomen and peritonitis. Permanent kidney damage may result from back-pressure during obstruction, leaving chronic kidney disease requiring lifelong management. Hyperkalemia, dangerously elevated blood potassium, can cause fatal cardiac arrhythmias. Recurrent obstruction occurs in a significant percentage of cases despite preventive measures. Surgical complications including infection, dehiscence, or stricture formation may develop following operative intervention. Gastrointestinal stasis secondary to pain and metabolic derangement is itself life-threatening in guinea pigs.