Puerperal Metritis (Acute Postpartum Metritis)

Puerperal metritis, also known as acute postpartum metritis, is a severe, life-threatening bacterial infection of the uterus occurring within the first 7 to 14 days after parturition, characterized by systemic illness, uterine inflammation, and a purulent or fetid vaginal discharge. In veterinary theriogenology, it is distinguished from endometritis (which is confined to the endometrium and typically occurs later) by the involvement of all uterine layers (endometrium, submucosa, and muscularis) and the presence of systemic signs such as fever, lethargy, anorexia, and dehydration. The condition arises from bacterial contamination of the uterine lumen during or after parturition, often due to retained fetal membranes, dystocia, obstetrical manipulation, or poor hygiene. The infection can rapidly progress to septicemia, endotoxemia, and peritonitis, posing a significant risk to the dam's life. In dairy cattle, puerperal metritis is a major cause of reduced fertility and economic loss, while in small animals (dogs and cats) it is less common but equally critical. The disease is classified as acute when clinical signs appear within 14 days postpartum, and chronic when signs persist beyond this period. The diagnosis relies on clinical examination, ultrasonography, and laboratory findings, and treatment involves aggressive systemic antibiotics, uterine lavage, and supportive care, with ovariohysterectomy reserved for severe cases or when future breeding is not desired.

The primary etiology of puerperal metritis is polymicrobial bacterial infection of the uterine lumen, with the most common isolates being Escherichia coli, Trueperella pyogenes, Fusobacterium necrophorum, and Prevotella melaninogenica in cattle. In dogs and cats, common pathogens include E. coli, Streptococcus spp., Staphylococcus spp., and Pasteurella spp. These bacteria are often introduced into the uterus during parturition from the environment, the dam's skin, or the gastrointestinal tract. Predisposing factors include retained fetal membranes, dystocia, obstetrical manipulation, cesarean section, and poor perineal hygiene. The bacteria colonize the compromised endometrium, which is denuded and necrotic after placental separation, and produce toxins such as lipopolysaccharide (LPS) from Gram-negative bacteria, leading to systemic inflammation. In addition to infectious agents, hormonal factors play a role: postpartum uterine involution is driven by oxytocin and prostaglandin F2alpha (PGF2α), and any disruption in these hormonal cascades can impair uterine clearance and immune defense. Uterine atony, often due to hypocalcemia or excessive uterine distension, allows bacterial proliferation. In some cases, iatrogenic factors such as contaminated obstetrical instruments or improper intrauterine infusions can introduce pathogens. The disease is not typically genetic, but certain breeds may have increased susceptibility due to conformational or anatomical factors (e.g., bulldogs with narrow pelvic canals). Environmental factors, including overcrowding, poor sanitation, and stress, also contribute to the risk of infection.

Puerperal metritis is most commonly reported in dairy cattle, with an incidence ranging from 10% to 20% of calvings, and it is a leading cause of postpartum morbidity and mortality. In beef cattle, the incidence is lower, around 5% to 10%. In dogs and cats, puerperal metritis is relatively rare, with an estimated incidence of less than 1% of whelpings, but it is more likely to occur in cases of dystocia, retained placentas, or cesarean sections. Breed predispositions in cattle include Holstein-Friesian, which have a higher incidence due to high milk production and associated metabolic stress. In dogs, breeds with a higher risk of dystocia, such as Bulldogs, Pugs, and Boston Terriers, may have an increased risk of metritis. Age is a factor: older cows (≥3 lactations) and older bitches (≥6 years) are more susceptible. Parity also plays a role, with primiparous animals being at higher risk due to a longer and more difficult parturition. The disease is more common in animals that have experienced retained fetal membranes, which occurs in about 5% to 10% of calvings and up to 20% in certain herds. Seasonal variations may exist, with higher incidence in winter when hygiene is harder to maintain. In breeding kennels, poor management practices, such as inadequate whelping box sanitation, can increase the risk. The economic impact is significant, leading to reduced milk production, increased culling, and veterinary costs.

The pathophysiology of puerperal metritis involves a complex interplay between bacterial invasion, uterine tissue damage, and systemic inflammatory response. After parturition, the uterus undergoes involution, a process characterized by myometrial contractions, endometrial regeneration, and elimination of bacteria. The uterine lumen is normally sterile, but during parturition, the cervix is dilated, allowing bacteria to ascend from the vagina and perineum. The endometrium is denuded and necrotic, providing a rich medium for bacterial growth. Bacteria such as E. coli adhere to the endometrial epithelium and produce adhesins and toxins, including LPS, which triggers a massive release of pro-inflammatory cytokines (TNF-α, IL-1, IL-6) from macrophages and neutrophils. This leads to local inflammation, vasodilation, and increased vascular permeability, resulting in edema and leukocyte infiltration. The infection can extend into the myometrium and serosa, causing metritis and perimetritis. Systemic absorption of LPS and bacteria leads to endotoxemia and septicemia, manifesting as fever, depression, and cardiovascular collapse. The inflammatory response also impairs uterine contractility by interfering with smooth muscle function, leading to uterine atony and retention of lochia and bacteria. In cattle, the presence of retained fetal membranes exacerbates the condition by providing a substrate for bacterial growth and delaying uterine involution. The release of PGF2α from the inflamed endometrium is disrupted, further impairing uterine clearance. In severe cases, the infection can spread to the peritoneum, causing peritonitis, or to the bloodstream, leading to septic shock and disseminated intravascular coagulation (DIC). Chronic inflammation can result in endometrial fibrosis, adhesions, and permanent infertility.

Several intrinsic and extrinsic factors predispose animals to puerperal metritis. Intrinsic factors include age, with older animals having reduced immune function and slower uterine involution. Parity is significant: primiparous animals are at higher risk due to a longer and more difficult parturition, which increases the likelihood of uterine trauma and retained fetal membranes. Hormonal imbalances, such as hypocalcemia (milk fever) in dairy cows, impair uterine contractility and immune response, predisposing to metritis. Genetic factors may play a role, as certain breeds (e.g., Holstein cattle) have a higher incidence, possibly due to selection for high milk production, which is associated with immunosuppression. Anatomical abnormalities, such as a narrow pelvic canal or uterine torsion, can lead to dystocia and subsequent metritis. Extrinsic factors include poor hygiene during parturition, such as contaminated bedding or inadequate cleaning of the perineum, which increases bacterial contamination. Obstetrical interventions, including manual delivery, use of obstetrical chains, or cesarean section, can introduce pathogens and cause uterine trauma. Retained fetal membranes are a major predisposing factor, as they provide a medium for bacterial growth and delay involution. Environmental stress, such as overcrowding, transportation, or heat stress, can suppress the immune system. Nutritional deficiencies, particularly of vitamin E, selenium, and beta-carotene, impair immune function and increase susceptibility to infection. In small animals, improper whelping management, such as failure to clean the whelping box or excessive handling of neonates, can increase the risk. Additionally, the use of corticosteroids or other immunosuppressive drugs during pregnancy may predispose to infection.

Clinical signs of puerperal metritis typically appear within the first 7 to 14 days postpartum and range from mild to severe. The hallmark sign is a purulent, often fetid, vaginal discharge, which may be brownish or reddish in color and may contain necrotic tissue. The discharge is usually present on the tail, perineum, or bedding. Systemic signs include fever (often >39.5°C or 103°F), lethargy, depression, anorexia, and decreased milk production in dairy animals. The animal may show signs of dehydration, such as sunken eyes and decreased skin turgor, and may have an increased heart rate and respiratory rate. In severe cases, signs of endotoxemia and septicemia develop, including cold extremities, weak pulse, and recumbency. Abdominal palpation may reveal an enlarged, doughy uterus, and in some cases, the uterus may be painful on palpation. In cattle, rectal palpation can detect a thin-walled, flaccid uterus with a purulent discharge. In dogs and cats, the vulva may be swollen, and the discharge may be noticed on the bedding or when the animal is examined. The dam may neglect her puppies or kittens, and there may be a decrease in milk production. In cases of peritonitis, abdominal distension and severe pain are evident. In chronic cases, the discharge may persist for weeks, and the animal may have a poor body condition. In some cases, the infection can lead to septicemia and death if not treated promptly. It is important to note that some animals may not exhibit a fever, especially in the early stages, so a high index of suspicion is necessary in postpartum animals with any systemic illness.

Differential diagnoses for puerperal metritis include: 1) Retained fetal membranes (RFM): RFM is characterized by the presence of fetal membranes protruding from the vulva for more than 12 hours after parturition. It can lead to metritis, but the primary sign is the visible membranes. In metritis, the membranes may be absent or partially retained. 2) Endometritis: Endometritis is a superficial inflammation of the endometrium that occurs later (after 21 days postpartum) and is not associated with systemic signs. Vaginal discharge is mucopurulent but the animal is otherwise healthy. 3) Vaginitis: Vaginitis is inflammation of the vagina, which can cause a purulent discharge but is not associated with systemic illness or uterine enlargement. 4) Pyometra: Pyometra is a chronic uterine infection that occurs during diestrus, typically in intact bitches, and is characterized by a closed cervix, abdominal distension, and systemic illness. It is not directly related to parturition. 5) Peritonitis: Peritonitis can be a complication of metritis, but it can also occur independently due to uterine rupture or other causes. It presents with severe abdominal pain, fever, and shock. 6) Septicemia: Septicemia can arise from metritis but can also be caused by other sources of infection, such as mastitis or wound infections. 7) Hypocalcemia (milk fever): In dairy cows, hypocalcemia can cause recumbency and depression, but it is not associated with a purulent discharge. 8) Dystocia: Dystocia is difficult parturition, which can lead to metritis, but the primary problem is the inability to deliver the fetus. 9) Uterine rupture: Uterine rupture is a rare but severe complication of parturition that can cause peritonitis and shock. It may be associated with a history of dystocia or obstetrical manipulation. 10) Mastitis: Mastitis is an infection of the mammary gland, which can cause fever and depression, but the udder is swollen and painful, and the milk is abnormal. A thorough clinical examination, including vaginal cytology, ultrasonography, and laboratory tests, is essential to differentiate these conditions.

The diagnostic algorithm for puerperal metritis begins with a thorough history and physical examination. The clinician should assess the time since parturition, the presence of risk factors (e.g., dystocia, retained fetal membranes), and the character of the vaginal discharge. A complete physical examination should include temperature, heart rate, respiratory rate, and assessment of hydration status. Abdominal palpation may reveal an enlarged uterus, but in large animals, rectal palpation is more informative. The next step is to perform a vaginal examination using a sterile speculum to visualize the discharge and cervix. Vaginal cytology can be obtained by swabbing the cranial vagina or cervix; in metritis, the cytology will show numerous neutrophils, bacteria, and necrotic debris. Blood work should be performed, including a complete blood count (CBC) and serum biochemistry. The CBC may show leukocytosis with a left shift, toxic neutrophils, and sometimes leukopenia in severe cases. Biochemistry may reveal azotemia, elevated liver enzymes, and electrolyte imbalances. Serum progesterone levels are typically low (<1 ng/mL) in the postpartum period, which helps rule out pyometra. Ultrasonography is a valuable diagnostic tool: transabdominal or transrectal ultrasound can assess uterine size, wall thickness, and the presence of intraluminal fluid. In metritis, the uterine wall may be thickened, and the lumen may contain echogenic fluid. In cattle, transrectal ultrasonography can also evaluate ovarian structures and the presence of a corpus luteum. Radiography is less useful but may be performed to rule out fetal retention or uterine rupture. Bacterial culture and sensitivity testing of the uterine discharge can guide antibiotic therapy, but treatment should be initiated before results are available. In cases where the diagnosis is uncertain, a uterine biopsy can be performed, but this is rarely necessary in the acute setting. The diagnostic algorithm should be systematic to ensure prompt and accurate diagnosis, as delayed treatment can be fatal.

Laboratory findings in puerperal metritis reflect systemic inflammation and infection. Hematology typically shows leukocytosis (increased white blood cell count) with a left shift (increased band neutrophils) and toxic changes in neutrophils (e.g., cytoplasmic vacuolation, toxic granulation). In severe cases, leukopenia may occur due to bone marrow exhaustion. Anemia may be present due to blood loss or hemodilution. Serum biochemistry often reveals dehydration (elevated total protein, albumin, and packed cell volume), azotemia (elevated blood urea nitrogen and creatinine) due to prerenal causes, and electrolyte imbalances, particularly hypocalcemia and hypokalemia. Liver enzymes (aspartate aminotransferase, gamma-glutamyl transferase) may be elevated due to hepatic hypoxia or endotoxemia. In cases of endotoxemia, blood glucose may be low. Serum progesterone levels are typically low (<1 ng/mL) in the postpartum period, confirming the absence of a functional corpus luteum. In cattle, acute phase proteins such as haptoglobin and serum amyloid A are elevated. Urinalysis may show proteinuria, hematuria, or casts due to renal involvement. Vaginal cytology is a key diagnostic test: in metritis, the smear will show numerous neutrophils, often degenerate, with intracellular and extracellular bacteria, and necrotic debris. The presence of parabasal and intermediate cells indicates a lack of estrogen stimulation, consistent with the postpartum period. Bacterial culture of the uterine discharge is essential for identifying the causative organisms and determining antibiotic sensitivity. Common isolates include E. coli, Trueperella pyogenes, and anaerobic bacteria. In dogs and cats, culture may yield E. coli, Streptococcus, or Staphylococcus. Blood cultures may be positive in septicemic cases. Histopathology of the uterus, if obtained, would show diffuse infiltration of neutrophils and macrophages, necrosis, and edema of the endometrial and myometrial layers.

Imaging plays a crucial role in the diagnosis and monitoring of puerperal metritis. Abdominal ultrasonography is the most commonly used modality in small animals and can also be performed transrectally in cattle. In dogs and cats, a transabdominal ultrasound can visualize the uterus, which is typically enlarged, with a thickened, hypoechoic wall. The uterine lumen may contain anechoic or echogenic fluid, and in some cases, gas artifacts may be seen due to gas-producing bacteria. The uterine wall may appear irregular or have a loss of normal layering. In cattle, transrectal ultrasonography is preferred, allowing assessment of uterine involution, the presence of fluid, and the ovarian structures. The uterine wall thickness is typically >2 cm in metritis, and the lumen may contain hyperechoic material. Ultrasonography can also detect complications such as uterine rupture or peritonitis, which would show free fluid in the abdomen. Radiography is less sensitive but may be used to rule out retained fetuses or fetal membranes. In cattle, radiography is rarely used due to the size of the animal. In small animals, abdominal radiographs may show an enlarged uterus with a soft tissue opacity, but this is not specific. Computed tomography (CT) and magnetic resonance imaging (MRI) are rarely used in veterinary practice for metritis but can provide detailed images of the uterus and surrounding tissues. Vaginoscopy, using a rigid or flexible endoscope, can visualize the vaginal and cervical mucosa, revealing hyperemia, discharge, and the presence of necrotic tissue. This can be useful for obtaining samples for culture and cytology. In summary, ultrasonography is the imaging modality of choice for diagnosing and monitoring puerperal metritis, providing real-time information on uterine size, content, and wall integrity.

Cytological and histopathological examination is essential for confirming the diagnosis of puerperal metritis and differentiating it from other uterine conditions. Vaginal cytology is a simple and rapid test that can be performed in the clinic. A sterile cotton swab is used to sample the cranial vagina or cervix, and the smear is stained with Diff-Quik or Wright's stain. In puerperal metritis, the cytology is characterized by a high number of neutrophils, many of which are degenerate (swollen, with fragmented nuclei). Bacteria may be seen intracellularly or extracellularly, and necrotic debris is often present. The presence of parabasal and intermediate epithelial cells indicates a lack of estrogen stimulation, which is expected in the postpartum period. The absence of superficial cells (cornified) helps rule out estrus. In chronic cases, macrophages and lymphocytes may be more prominent. Histopathology of the uterus is rarely performed in live animals but may be obtained during ovariohysterectomy or postmortem. Grossly, the uterus is enlarged, edematous, and may have a necrotic endometrium. Microscopically, there is diffuse infiltration of neutrophils and macrophages into the endometrium and myometrium, with necrosis, hemorrhage, and edema. The endometrial glands may be dilated and filled with inflammatory exudate. In severe cases, there is myometrial necrosis and thrombosis of blood vessels. Special stains, such as Gram stain, can help identify the type of bacteria. Immunohistochemistry may be used to detect specific pathogens, such as E. coli antigens. In cattle, endometrial cytology obtained by cytobrush is used to diagnose subclinical endometritis, but in acute metritis, the cytology is more dramatic. Histopathology is the gold standard for confirming the extent of inflammation and tissue damage, but it is not practical in the acute clinical setting.

Treatment of puerperal metritis requires a multi-modal approach aimed at eliminating the infection, supporting the systemic condition, and promoting uterine involution. The first step is emergency stabilization, especially in animals with severe systemic signs. Intravenous fluid therapy with balanced electrolyte solutions (e.g., lactated Ringer's solution) is essential to correct dehydration and electrolyte imbalances. In cases of hypocalcemia, calcium gluconate (10% solution) should be administered slowly IV at a dose of 0.5-1.0 mL/kg, with cardiac monitoring. Non-steroidal anti-inflammatory drugs (NSAIDs) such as flunixin meglumine (1.1 mg/kg IV or IM) or meloxicam (0.2 mg/kg IV or SC) are used to reduce inflammation and fever, but caution is needed in dehydrated animals due to renal risks. Systemic antibiotics are the cornerstone of treatment. In cattle, a common choice is ceftiofur (2.2 mg/kg SC q24h for 3-5 days) or oxytetracycline (10-20 mg/kg IV or SC q24h). In dogs and cats, amoxicillin-clavulanate (12.5-25 mg/kg PO q8-12h) or enrofloxacin (5-10 mg/kg PO or IM q24h) may be used, but combination therapy is often recommended to cover Gram-negative and anaerobic bacteria. Antibiotic selection should ideally be based on culture and sensitivity, but treatment should be initiated immediately. Uterine lavage with warm sterile saline or dilute povidone-iodine solution (0.1%) can be performed in cattle to remove purulent material, but it is controversial in small animals due to the risk of spreading infection. Uterine lavage should be followed by the administration of oxytocin (20-40 IU IM or IV in cattle; 0.5-2 IU IM in dogs) to stimulate uterine contractions and expel debris. Prostaglandin F2α (dinoprost tromethamine) can be used in cattle (25 mg IM) to induce luteolysis if a corpus luteum is present, but in the postpartum period, it is less effective. In dogs, PGF2α (cloprostenol 1-2 μg/kg SC) may be used to promote uterine evacuation, but it is not recommended in severe cases due to the risk of uterine rupture. In cases of retained fetal membranes, manual removal is not recommended, but the membranes may be left to slough. Surgical intervention, specifically ovariohysterectomy, is indicated in cases of uterine rupture, peritonitis, or when medical treatment fails, especially in small animals. Supportive care includes nutritional support, warmth, and nursing care. The prognosis is good with prompt treatment, but severe cases can be fatal.

The prognosis for puerperal metritis depends on the severity of the infection, the timeliness of treatment, and the presence of complications. In mild to moderate cases, with early and aggressive treatment, the prognosis is good, and the animal is expected to recover fully. In dairy cattle, recovery is often associated with a return to normal milk production and fertility, although there may be a delay in conception. In severe cases with systemic involvement, such as septicemia or peritonitis, the prognosis is guarded to poor, and mortality rates can be high, especially if treatment is delayed. Negative prognostic indicators include a prolonged duration of clinical signs, the presence of toxic neutrophils on blood smear, severe dehydration, and the development of complications such as uterine rupture or DIC. In small animals, the prognosis is generally good if ovariohysterectomy is performed early in severe cases, but future fertility may be compromised if the uterus is preserved. In cattle, the impact on fertility is significant: cows with metritis have a higher risk of subsequent endometritis, delayed first ovulation, and reduced conception rates. The recurrence risk is low if the underlying predisposing factors are addressed. Long-term, the animal may have a reduced milk yield in the current lactation, but subsequent lactations are usually unaffected. In breeding animals, it is important to monitor for chronic endometritis, which can cause infertility. Overall, with appropriate treatment, the short-term survival rate is high, but the long-term reproductive performance may be affected.

Follow-up care for puerperal metritis is crucial to ensure complete resolution and to monitor for complications. After initial treatment, the animal should be re-examined within 48-72 hours to assess clinical improvement. The temperature, heart rate, and respiratory rate should be monitored, and the vaginal discharge should be evaluated for changes in color, odor, and quantity. In cattle, transrectal ultrasonography can be performed to assess uterine involution and the presence of fluid. The uterine wall thickness should decrease over time, and the lumen should become empty. In small animals, abdominal ultrasonography can be used to monitor uterine size and content. Serial blood work, including CBC and biochemistry, should be performed to monitor for resolution of leukocytosis and improvement in organ function. Serum progesterone levels can be measured to confirm the absence of a corpus luteum and to monitor the return to normal cyclicity. Vaginal cytology can be repeated to assess the reduction in neutrophils and bacteria. In breeding animals, a breeding soundness examination should be performed before the next estrus, including uterine culture and cytology to rule out chronic endometritis. In dairy cattle, a postpartum examination at 30-45 days is recommended to assess uterine involution and ovarian activity. If the animal is intended for breeding, a plan should be made for the next estrus, and any underlying predisposing factors, such as poor hygiene or nutritional deficiencies, should be addressed. In cases where ovariohysterectomy was performed, the surgical site should be monitored for healing, and the animal should be restricted from activity for 10-14 days. The owner should be advised to monitor for any signs of recurrence, such as fever, lethargy, or abnormal discharge, and to seek veterinary care immediately if these occur.

Clinical pearls: 1) In postpartum animals, any fever or systemic illness within the first 14 days should raise suspicion for metritis, even in the absence of a visible discharge. 2) A fetid, purulent vaginal discharge is pathognomonic for metritis, but the absence of discharge does not rule out the disease, especially in cases of a closed cervix. 3) Ultrasonography is essential for assessing uterine contents and wall thickness; a uterine wall thickness >2 cm in cattle is suggestive of metritis. 4) In dairy cattle, hypocalcemia is a common concurrent condition; always check calcium levels and treat with calcium gluconate if low. 5) Antibiotic therapy should be initiated immediately with a broad-spectrum antibiotic, and culture results should be used to adjust therapy. 6) Oxytocin can be used to promote uterine evacuation, but it should not be used in cases of uterine rupture or if the cervix is closed. 7) In small animals, ovariohysterectomy is the definitive treatment for severe metritis, especially if the animal is not intended for breeding. 8) Prostaglandin F2α is not effective in the immediate postpartum period because there is no corpus luteum; it is more useful for pyometra. 9) Always monitor for signs of endotoxemia, such as cold extremities, tachycardia, and weak pulse, and treat aggressively with fluids and NSAIDs. 10) In cattle, retained fetal membranes should not be manually removed; instead, focus on antibiotic therapy and supportive care. Pitfalls: 1) Delaying treatment while waiting for culture results can be fatal; start empirical antibiotics immediately. 2) Using corticosteroids to treat shock can worsen the infection; use NSAIDs instead. 3) Performing uterine lavage in small animals can cause peritonitis if the cervix is closed; avoid it in dogs and cats. 4) Administering oxytocin in cases of uterine rupture can cause further damage; always rule out rupture with ultrasound. 5) Failing to correct hypocalcemia can lead to poor uterine contractility and persistent infection. 6) Using PGF2α in a postpartum animal with a closed cervix can cause uterine rupture. 7) Not providing adequate fluid therapy can lead to renal failure and worsening of the condition. 8) In dairy cattle, not monitoring for ketosis, which often accompanies metritis, can delay recovery. 9) In small animals, not considering pyometra as a differential, especially in intact bitches, can lead to misdiagnosis. 10) Discharging the animal too early without follow-up can result in recurrence or chronic endometritis.

Current drug protocols for puerperal metritis are based on Plumb's Veterinary Drug Handbook and theriogenology guidelines. In cattle: 1) Ceftiofur hydrochloride (Excede) 2.2 mg/kg SC q24h for 3-5 days, or ceftiofur crystalline free acid (Excede) 6.6 mg/kg SC as a single dose. 2) Oxytetracycline (LA-200) 10-20 mg/kg IV or SC q24h, but avoid IM due to tissue irritation. 3) Flunixin meglumine (Banamine) 1.1 mg/kg IV or IM q24h for 1-3 days. 4) Calcium gluconate 23% solution: 500 mL IV slowly (cattle) for hypocalcemia. 5) Oxytocin: 20-40 IU IM or IV, can be repeated q2-4h for 2-3 treatments. 6) Prostaglandin F2α (dinoprost tromethamine, Lutalyse) 25 mg IM, but only if a corpus luteum is present (rare in postpartum). 7) Intrauterine antibiotics are not recommended due to poor efficacy and risk of irritation. In dogs and cats: 1) Amoxicillin-clavulanate (Clavamox) 12.5-25 mg/kg PO q8-12h for 7-14 days. 2) Enrofloxacin (Baytril) 5-10 mg/kg PO or IM q24h, but use caution in young animals due to cartilage effects. 3) Metronidazole 10-15 mg/kg PO q12h for anaerobic coverage. 4) Flunixin meglumine 1.1 mg/kg IV or IM q24h, or meloxicam 0.2 mg/kg IV or SC once, then 0.1 mg/kg PO q24h. 5) Oxytocin 0.5-2 IU IM, but only if the cervix is open and no evidence of rupture. 6) Prostaglandin F2α (cloprostenol, Estrumate) 1-2 μg/kg SC q24h, but only in mild cases and with caution. 7) For severe cases, ovariohysterectomy is the treatment of choice. Supportive care includes IV fluids (Lactated Ringer's solution) at 60-90 mL/kg/day in dogs, and 40-60 mL/kg/day in cats, with potassium chloride supplementation as needed. Always adjust dosages based on the animal's condition and renal function.

The literature on puerperal metritis is extensive, particularly in dairy cattle. Key studies have established the role of E. coli and Trueperella pyogenes in the pathogenesis, with E. coli being the primary pathogen in the first week postpartum, and T. pyogenes becoming more prevalent later. Research by Sheldon et al. (2006) demonstrated that uterine disease is associated with an increased risk of infertility, and that cows with metritis have a lower conception rate. A meta-analysis by LeBlanc et al. (2002) found that metritis reduces the probability of conception by 20% and increases the risk of culling. The use of ceftiofur for the treatment of metritis has been supported by multiple studies, including a randomized controlled trial by Chenault et al. (2004), which showed that ceftiofur crystalline free acid was effective in resolving metritis. The role of PGF2α in the treatment of metritis is controversial; a study by Haimerl et al. (2012) found no benefit of PGF2α in cows with metritis, but it may be useful in cases with a corpus luteum. In small animals, the literature is less extensive, but a retrospective study by Fieni et al. (2014) reported that ovariohysterectomy is the most effective treatment for pyometra, and similar principles apply to metritis. The use of aglepristone (a progesterone receptor antagonist) has been investigated for the medical management of pyometra, but its role in metritis is limited. Consensus guidelines from the American College of Theriogenologists (ACT) and the European Society for Small Animal Reproduction (EVSSAR) recommend early intervention with systemic antibiotics and supportive care, and surgical removal of the uterus in severe cases. Overall, the evidence supports a multimodal approach, with antibiotics, anti-inflammatory drugs, and fluid therapy being the mainstays of treatment, and surgery reserved for refractory cases.