13
Blood administration
Blood must be given at body temperature to avoid hypothermia. An in-line filter is used as part of the administration set, to prevent small clots entering the bloodstream. Blood may be given extremely rapidly (over a few minutes) in cases of severe acute haemorrhage, or otherwise over a period up to 4 hours, as required. If there are concerns about circulatory overload, and administration is deemed to be needed at a slower rate, the total volume of fresh blood should not be held at body temperature for >4 hours to avoid bacterial growth, and should instead be refrigerated at 5°C and rewarmed as needed. Blood may be given into the jugular vein or a large diameter peripheral vein, or via the intra-osseous route if no veins are available, which can be cannulated with a 22 G or larger bore catheter (to avoid lysis of red cells).
Donor monitoring
Baseline monitoring of temperature, pulse (rate and quality), respiration, mucous membrane colour and capillary refill time, PCV and general clinical appearance should be performed, and repeated at least every 30 minutes during and immediately after transfusion. The patient should be monitored continuously for the first 15 minutes, during which the administration rate should be no greater than 0.5 ml/kg/h, unless urgent trans-fusion is needed. Transtrans-fusion reactions are rare and cannot be prevented or minimized by prior administration of steroids or antihistamines. The PCV should be measured 1 hour after administra-tion to determine the response, and thus the need for further transfusions.
Cross-matching
Blood groups have been studied in the rabbit.
However, their full significance is unclear, and
some form of cross-matching should always be performed. One-off transfusions are generally considered safe. Related rabbits are likely to be more compatible (Joysey, 1955). Haemolysis is the most common transfusion reaction but is impossible to predict without sampling large volumes (2 ml). If this is not practical, then aggluti-nation testing is performed: two drops of plasma from one rabbit are mixed with one drop of blood from the other rabbit on a room temperature microscope slide, and left for 1 minute. The pres-ence of visible agglutination suggests incompati-bility (Lichtenberger, 2004a,b).
Volume required
The volume of blood required will depend on the degree of blood loss, the pre-transfusion PCV, the size of the rabbit, and any ongoing losses, as well as the donor PCV. Ideally, a post-transfusion PCV of >30% should be aimed for, in order to correct acute haemorrhagic blood loss. As a general rule of thumb, 2 ml/kg of whole blood will increase the recipient PCV by 1%. The formula below (Platt and Garosi, 2012) may also be used:
Blood required (ml) = bodyweight of recipient (kg)
× circulating blood volume (66 ml/kg) × (desired recipient pre trans si n d n r Autotransfusion
Autotransfusion may be employed following intra-operative blood loss, e.g. following vena cava perf-oration during liver lobectomy. It is important to filter and anticoagulate blood in these situations. The ease of collection, avoidance of disease risk and lack of detrimental effects on a donor are advantages. The main disadvantage is the low thrombocyte count in autotransfused blood, and subsequent effects on clotting (Silva et al., 1984).
Anatomy
The normal anatomy of the abdomen is illustrated radiographically in Chapter 7, ultrasonographically in Chapter 8 and diagrammatically in Figure 13.1.
Indications for laparotomy
Abdominal trauma (including iatrogenic) Exploratory laparotomy is the standard of care in cases with a history of significant abdominal trauma, where there is a reasonable suspicion of internal organ damage (e.g. road traffic accident; attack by a medium-sized to large dog; blunt force trauma such as being trodden on or kicked by a human or large animal; recent intra-abdominal surgery, such as ovariohysterectomy, recent laparoscopy). Any case where there is evidence of intra-abdominal bleeding, bladder or gastrointestinal tract rupture should be investigated by exploratory laparotomy. This includes any laparoscopic procedure where there is a reasonable suspicion of iatrogenic organ damage, which may require conversion to laparotomy.
Exploratory laparotomy should be carried out with out delay in haemodynamically unstable trauma patients suffering from haemoperitoneum. These ani-mals are likely to have intraperitoneal bleeding from the liver, uterus, spleen or mesentery.
Exploratory laparotomy should be carried out following immediate patient stabilization in trauma patients with suspected urogenital or gastrointesti-nal tract rupture.
Acute-onset abdominal pain or discomfort Any acute-onset abdominal pain or discomfort with clinical findings suggestive of intra-abdominal pathology should be evaluated promptly following immediate patient stabilization and a minimum data-base and, depending on the findings, exploratory laparotomy may be indicated. Causes may include ruptured abdominal organ, peritonitis, gastrointest-inal obstruction, ureteral blockage, liver lobe torsion, uterine torsion and bladder rupture, which are discussed in the relevant chapters.
A full clinical history should be taken, including reproductive status and expected parturition date if
Stomach (covered
by omentum) Spleen Small
intestine Mesovarium
Ovary Uterus
Bladder
Midline spay incision site Exploratory laparotomy midline incision site Caecum
Caecum Paracostal
incision site Left medial
lobe of liver Left lateral lobe of liver
Rib position
Proximal colon Mesometrium kidneyLeft
(a)
The normal anatomy of the abdomen: (a) left lateral view; (b) right lateral view.
13.1
Small intestine
Caecum Distal colon Caudal process of
caudal lobe of liver
13th rib Kidney Omentum
Stomach
Exploratory laparotomy midline incision site
Paracostal incision site
Right lobe of liver Caecum
Proximal colon Midline spay
incision site
Duodenum Bladder
(b)
pregnant, breed type, recent exertion, dental health status, food and treats offered, potential foreign body ingestion (e.g. fur mats, carpet fibres, clay-based cat litter, locust bean pods) and a prior history of gastrointestinal stasis. Appetite, passage of faeces, caecotrophs and urine should be noted. Impending parturition, especially in an obese doe, may be asso-ciated with pregnancy toxaemia and elective caesar-ean or ovariohysterectomy may be necessary.
Deep-chested large breeds such as French Lops and some Dwarf Lops appear over-represented as liver lobe torsion cases, as do rabbits that have ad recent e erti ns e ni t ri t’ d e t pred ators. Rabbits with dental disease and a poor state of grooming are predisposed to fur mat ingestion.
Rabbits with a prior history of gastro intestinal stasis may have had intermittent partial obstructions previously, increasing the index of suspicion of
current total obstruction. Recent oliguria may indi-cate bladder rupture or outflow obstruction.
Abdominal radiography and ultrasonography are extremely helpful in making the decision whether and when to perform an exploratory laparotomy. In cases of suspected intra-abdominal bleeding or liver lobe torsion, serial PCV measurement may provide an assessment of haemodynamic stability. In cases of suspected gastrointestinal foreign body, serial radiography and serum glucose measurement pro-vide indicators of the presence or lack of successful progression of a foreign body through the gastro-intestinal tract, and help determine the need for exploratory laparotomy. The presence of a PCV below 25%, and raised liver enzymes in an acutely anorexic and collapsed or lethargic rabbit is strongly indicative of liver lobe torsion (Saunders et al., 2009;
Wenger et al., 2009). The presence of serum glu-cose measurements above 20 mmol/l in an acutely anorexic and collapsed or lethargic rabbit is strongly indicative of small intestinal obstruction (Harcourt-Brown and Harcourt-(Harcourt-Brown, 2012).
Peritonitis (± ruptured viscus)
Peritonitis may be suggested by a history of recent trauma, surgery, gastrointestinal foreign body, urinary tract blockage or internal abscessation. There may be radiographic evidence of peritonitis (ground glass appearance and/or pneumoperitoneum), or ultrasound evidence (free fluid and/or gas), although these are not definitively diagnostic. Abdominal tap or diagnostic peritoneal lavage evidence of ruptured vis-cus is strongly indicative, but false negatives (insuffi-cient or inaccessible fluid present) and false positives (iatrogenic viscus penetration) are both possible.
Abdominocentesis is potentially complicated in the rabbit by the high risk of perforation of the gut or bladder. This risk is greater in an animal with gas distension of the stomach or caecum, or a distended urinary bladder, and is therefore ideally carried out in dorsal recumbency, allowing the abdominal vis-cera to fall away from the site of needle entry.
However, in this position, free fluid is also displaced away from the ventrum, so sample recovery is extremely poor. The voluminous gastrointestinal tract may block or enfold the needle or catheter, giving a negative finding, especially if the volume of fluid is small. In practice, ultrasound-guided abdominocentesis is a more precise, effective and potentially safer tool. An appropriately sized needle (typically 23 G, 1 inch) or catheter is introduced through an aseptically prepared site at right angles
to the body wall, just lateral to the ventral midline, and caudal to the umbilicus. A syringe may be used to withdraw a sample, or fluid may be allowed to drip from the needle hub (Fox, 2011).
Diagnostic peritoneal lavage is more likely to obtain meaningful results than blind abdominocen-tesis. The technique is as described for abdomino-centesis, using an over-the-needle catheter. After introduction of the catheter, the stylet is removed, aspiration is attempted and, if no fluid is present, 20 ml/kg of warm sterile 0.9% saline is introduced slowly. Alternatively, a small midline skin incision may be made, and a larger bore catheter inserted, which is more invasive but less liable to produce false-negative results. A bung or three-way tap is placed on the catheter, and the rabbit is then gently rolled from side to side to disperse the fluid evenly throughout the abdominal cavity. A syringe may be used to withdraw a sample, or fluid may be allowed to drip from the catheter hub. Only a small propor-tion of the total instilled fluid is expected to be retrievable by this method (Fox, 2011).
Sedation or anaesthesia may be employed as required. In the collapsed animal it may not be nec-essary or appropriate to use chemical restraint.
Local anaesthetic infiltration of the sampling site may also be performed.
Samples may be evaluated in a number of ways:
• Gross examination for the visual appearance of blood or gut contents or olfactory evidence of urine or gut content
• Biochemical analyses, such as:
Dipstick tests (e.g. Multi-Stix, Bayer) for the presence of blood
pH measurement
Serum biochemistry analysis for the presence of urea
Refractometry to quantify specific gravity in undiluted samples more accurately
• Cytological examination is helpful in diagnosing gastrointestinal rupture, bladder rupture, exfoliative neoplasia, and inflammatory or infectious conditions
• Bacterial culture and sensitivity, including anaerobic culture, may be performed in cases of bacterial peritonitis.
Samples may then be defined as transudate, modified transudate or exudate. The presence of urea is strongly indicative of bladder rupture, and an acidic pH is indicative of stomach rupture.
Gastrointestinal, urogenital or other administration of barium-based positive contrast medium is absolutely contraindicated in suspected cases of hollow organ rupture, as it may provoke a severe chemical peritonitis.
Exploratory laparotomy is performed as des-cribed to examine the extent of the lesion(s) visually. Fluid is removed by suction to allow
Treatment of organ rupture/secondary bac terial and sterile chemical peritonitis
visualization of the abdomen systematically. Even if a lesion is detected, a full examination should be carried out, in case other lesions are present. If possible, the affected area is isolated to prevent further contamination.
Hollow organ ruptures should be closed at this point. This may be achieved via a simple closure (e.g. gastrointestinal tract, bladder). If the site is
Chronic abdominal discomfort and gastrointestinal stasis
Chronic continuous or intermittent abdominal pain or gastrointestinal stasis may indicate a number of pathological conditions such as neoplasia, internal abscessation, uterine pathology, or abdominal ad hesion formation. Whilst many of these will be diagnosed on imaging modalities such as ultra-sonography or radiography, a full visual examin ation of the abdomen may be required for definitive diag-nosis by examination and biopsy as necessary, and treatment, if possible.
Investigation of urogenital tract haemorrhage
Urogenital tract haemorrhage, in either sex, may be associated with neoplasia, infection, or adhe-sion formation anywhere along the urinary (Figure 13.2) and genital tracts. In the entire doe, endometrial venous aneurysm is an additional not sufficiently viable to allow this (e.g. necrotic gastrointestinal tract), resection (enterectomy) is appropriate. The prognosis in such a case is significantly worse than for a more recent breach of an internal organ, with a lower degree and/or duration of contamination, and less risk of repeated contamination due to organ wound breakdown.
Bladder wall rupture repair should involve debridement of any tissue of questionable viability, taking care to avoid damage to the ureters. The bladder is closed in a single or double layer (McGrotty and Doust, 2004).
In ruptures of internal abdominal abscesses or abscessated structures, e.g. ovaries, complete re-moval of the infected area and associated organ, where possible, is ideal.
Samples of any abdominal contamination are obtained and submitted for cytology and aerobic and anaerobic bacterial culture and sensitivity.
Broad spectrum antibiosis (as discussed in Chapter 29) is initiated, ideally via the intravenous route, pending results.
Urine, even if sterile, provokes a chemical peritonitis, particularly in the rabbit, due to its high sediment content. Bile is also capable of provoking a severe inflammatory response.
Any foreign, necrotic or fibrinous material is debrided and removed. The abdomen is thoroughly but gently lavaged with large volumes of warmed is t nic l ids lactated in er’s r is t nic saline 200–300 ml/kg or sufficient to lavage until the fluid removed is clear, whichever is the greater).
Suture material used to close organs and the abdominal wall should be monofilament, to reduce the risk of bacterial infiltration in the fibres, and materials that provide support for a longer duration may be selected due to prolonged healing in peritonitis cases (e.g. polydioxanone II).
Catgut is contraindicated due to its rapid degradation in the presence of inflammation (McGrotty and Doust, 2004).
Open peritoneal drainage (OPD) may also be employed. However, whilst the survival rates in domestic carnivores are similar (Staatz et al., 2002), animals undergoing OPD require much longer periods of hospitalization, and greater medical inter-vention, including blood transfusion and enteral feeding, and this author favours primary closure.
Heparin treatment via lavage fluid to reduce fibrin formation is controversial. It has been shown to improve survival in dogs with experimental peritonitis, but may lead to reduced tissue perfusion due to red cell aggregation.
differential. In the neutered doe, cervical or vaginal vestibular stump pathology may be present. In the male rabbit, prostatic pathology is a rare but reported condition. Abdominal and thoracic radio-graphy, and abdominal ultrasound examination are indicated to assist in localizing the lesion and assessing organ architecture to complement and precede exploratory lapar otomy. Contrast studies may be required, including excretory urography (see Chapter 3).
Investigation of ovarian remnant
Ovarian remnant syndrome may be noted in neu-tered female rabbits. The friability of the ovary and oviduct, especially in sexually immature rabbits, allows incomplete gonadectomy to occur (see Chapter 12). Ovarian tissue may also attach and revascularize to any intra-abdominal surface, effec-tively autotransplanting itself. In cases of suspected ovarian remnant, a full and complete examination of the abdominal cavity is required to ensure that all remnants are found and removed. An ovarian rem-nant may be suspected on history of hypersexuality and continuing oestrus behaviour in a neutered female rabbit, and confirmed on dynamic hormonal testing (progesterone–human chorionic gonado-tropin stimulation test; Kellie et al., 2007; Varga, 2011; see also Chapter 20).
Adrenal gland disease
Adrenal gland disease has been reported in neu-tered male rabbits, and may potentially occur in neutered female rabbits and entire animals (see Chapter 20).
Mass adherent to bladder wall, causing persistent haematuria.
13.2
signs on radiography. Where there has been urine leakage from the vaginal vestibulum, cystic fluid accumulations may be seen filling a space created by adhesions and fibrous tissue. Where adhesions have obstructed the ureters, ureteral dilatation prox-imal to the lesion, and hydronephrosis, may be seen (see Chapters 11 and 12).
Hernia and dehiscence repair
Revision surgery, following significant suture reac-tion, postoperative infecreac-tion, partial or complete breakdown of the midline incision, eventration, herniation or dehiscence, is not an uncommon requirement in the rabbit. In the majority of cases the repair will be superficial only, but any suspicion of gut or other viscera herniation or entrapment, adhesion formation or peritonitis will necessitate an exploratory laparotomy.
Site and length of incision Singular approaches
Whilst theoretically there are a number of ap-proaches to the abdomen, in the vast majority of cases the ventral midline approach is favoured (see Figure 13.1 and Operative Technique 13.1). The main advantage of this approach is the excellent bilateral exposure to almost any area within the abdomen, depending on the length and position of incision, which may be easily extended as necessary either cranially to the xiphisternum and/or caudally to the pelvic symphysis. An incision through the linea alba is less painful postoperatively than incision through muscle, easier to repair, and produces less peri-operative bruising and seroma formation.
The length and position of incision depends on the site of interest, with the approach to the liver or stomach only necessitating an approach from the umbilicus extending cranially to the xiphisternum, and the approach to the bladder or uterus from the umbilicus extending caudally or just cranial to the pelvic brim. These may need to be extended appro-priately to view the remainder of the abdominal con-tents, or to gain better exposure, especially in deep-chested rabbits. It may be quicker and simpler in many cases to make a full-length incision at the outset, if this is anticipated to be necessary, although the shortest incision allowing adequate vis-ualization is advised. Visual examination of the abdominal viscera, particularly the gastrointestinal tract, (with minimal handling and displacement) is preferable in the rabbit, and so a larger incision and less exteriorization of internal organs is advisable compared with the cat or dog.
The paramedian incision is less often used as it does not permit easy access to the contralateral side, and the muscle incision is more painful to make, more difficult to close, and has a greater inci-dence of complications. The key advantage in dogs, that it avoids dissection underneath the prepuce, is not a concern in the male rabbit due to the more caudally positioned penis. A flank approach is gen-erally not employed, for the same reasons.
Exploration of adhesions involving the bladder.
Note the use of suction to avoid abdominal contamination with urine.
13.3
Organ biopsy
Exploratory laparotomy may be required for visual examination and biopsy of one or more organs within the abdominal cavity. The liver is the most commonly investigated organ (see Operative Technique 13.2), but the bladder, kidneys, pancreas, adrenal glands, gastrointestinal tract, visually abnormal intra-abdom-inal fat and any abdomintra-abdom-inal mass (abscess, neo-plasia, etc.) may require exploration.
Myiasis
Myiasis, where there is entry or suspected entry into the abdominal cavity, is an indication for exploratory laparotomy to diagnose and treat any resultant peri-tonitis and foreign body reaction. Prior imaging may be helpful.
Retroperitoneal bleeding
Retroperitoneal bleeding is extremely uncommon given the low incidence of road traffic accidents involving domestic pet rabbits, but may be seen rarely, e.g. in conjunction with vertebral fracture.
Investigation of suspected adhesion formation
Adhesions may be suspected in cases of chronic continuous or intermittent gastrointestinal motility disorders, urine scalding or urinary incontinence, repeated urinary tract infections or episodic abdom-inal pain. Radiography and ultrasonography may be unrewarding and non-specific given the relatively small size of some adhesions, and the difficulty in differentiating them from solid masses in larger ones (Figure 13.3). Bladder or bowel malpositioning may be visible. Pockets of gas diffusely positioned through the gastrointestinal tract may be the only
The paracostal approach, parallel and caudal to the last rib, is rarely employed in the rabbit.
Gastropexy, although often required in domestic carnivores, is rarely performed in the rabbit, and more complete access to the stomach and gastro-intestinal tract is required in this species.
Gridiron dissection is generally recommended for incisions through muscle layers, to avoid trauma through muscle fibres. However, this limits the pos-sible size of the incision, making it generally imprac-tical (Anderson, 2005).
Combined approaches
A combined approach is rarely required. A com-bined ventral midline and paracostal approach may be employed for improved access to deeper liver lobe lesions, but is more painful, with a greater inci-dence of postoperative wound complications.
Organ handling
The organs, particularly the gastrointestinal tract, should be handled as little and as gently as possi-ble. Where possible the gastrointestinal tract should be examined for lesions in situ, avoiding unneces-sary organ handling due to the risks of temperature loss, adhesion formation and ileus (see Chapter 11).
However, when fully examining the gastrointestinal tract, it will be necessary to remove it from the abdomen, in which case it should be kept warm and moistened whilst exteriorized (Figure 13.4). It should be replaced so as to avoid undue folding of gas-filled sections, especially the caecum, to avoid causing pain and inhibiting the passage of gas and ingesta.
Potential problems and how to avoid them
Adhesion formation
Adhesion formation (see also Chapter 11) is the main potential postoperative complication of any laparotomy (Ray et al., 1998). Rabbits are extremely prone to adhesion formation, and are used as a lab-oratory model (McDonald et al., 1988). Adhesions may develop in response to any source of trauma, irritation or inflammation of any tissue (in this case, within the abdomen). The peritoneum, bladder, uterus or uterine stump, and intestines are the most common sites of adhesion formation. Both laparo-tomy and laparoscopy result in a similar incidence of adhesions, where the surgical procedure is other-wise the same (Becker and Stucchi, 2004).
Initiating causes are primarily associated with handling and exposure of tissues. Minor abrasions to the serosal or subserosal surfaces of any internal organ result in fibrin deposition, potentially allowing two areas of tissue to become adherent. This pro-cess starts within hours of the original insult.
The caecum has been exteriorized to investigate chronic distension and avoid contamination of the abdomen, but must be kept warm and moist and re-placed carefully.
13.4
Risk factors for adhesion formation
• Any handling of tissue that causes even the most minor trauma (e.g. use of rat-toothed forceps on tissues, the use of dry swabs to clean a surface of blood causing minor abrasions, the use of dry gloved hands).
• Excessive dryness of tissues (e.g. drying out under hot operating lights), or thermal damage from cautery or electrosurgery equipment.
• Chemical irritants (e.g. powder from gloves, excessive suture material remnants, or urine contamination of the abdomen).
• The presence of infection.
• Any devitalized or necrotic tissue or exposed serosal surfaces (e.g. the cervical stump/
vaginal vestibulum following ovariohysterectomy).
Surgery is not the only potential cause of adhe-sions. Any abdominal contamination (e.g. following bladder or intestinal content leakage, or intra-abdominal abscessation rupture) may lead to adhe-sion formation and should be rapidly addressed by exploratory laparotomy, closure of the organ, and thorough lavage of the abdomen (Figure 13.5).
Progression to permanent adhesions is not inevi -table, but is more likely if tissues are compromised by drying and/or poor handling. Collagen is laid down in the fibrinous adhesions to produce fibrous adhesions, which may remain clinically silent or may cause chronic health issues. Depending on the organ systems involved, adhesions may cause problems in gut motility by preventing the free movement of gut within the abdomen, or constrict-ing it to the point where gut content cannot pass freely (Figure 13.6).
Adhesions may affect bladder position or mobil-ity, constrict bladder emptying, or may partially or completely obstruct the ureters to cause proximal