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Compendium June 2010 (Vol 32, No 6)

Surgical Views — Suspensory Ligament Rupture Technique During Ovariohysterectomy in Small Animals

by Lawrence N. Hill, DVM, DABVP, Daniel D. Smeak, DVM, DACVS

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    Abstract

    During ovariohysterectomy, suspensory ligament (SL) rupture permits retraction of the ovary and distal ovarian pedicle through a limited ventral midline incision. This allows the surgeon to confirm that the pedicle is securely double ligated and includes no ovarian remnant. For less experienced surgeons, SL rupture is often difficult and daunting because the ligament is buried within the abdominal viscera and must be identified blindly by palpation. Furthermore, in dogs, the ligament must be digitally disrupted, which may cause hemorrhage and serious injury to surrounding structures such as the ovarian pedicle. This article describes step-by-step techniques to disrupt the SL in dogs and cats. We have found that these techniques can be taught easily and successfully to novice surgeons.

    Ovariohysterectomy is the most common elective surgical procedure performed by small animal practitioners.1,2 In young, healthy patients, the technique can be performed safely through a small ventral midline laparotomy incision to save time and reduce trauma. This limited approach makes exposure of the ovarian pedicle for ligation one of the most challenging aspects of ovariohysterectomy, particularly for inexperienced solo surgeons. Exposure is vitally important because the surgeon must ensure that the pedicle is securely double ligated and includes no ovarian remnant. In dogs and cats, the suspensory ligament (SL) tethers the ovary to the dorsal abdominal cavity.

    SL rupture is performed only when it is not possible to expose enough ovarian pedicle for safe ligation. In some dogs and cats—particularly animals that are pregnant or have an enlarged uterus—and depending on the extent of the abdominal approach, it is possible to expose enough ovarian pedicle for ligation without SL rupture. However, SL rupture is usually required to allow retraction of the ovary and distal ovarian pedicle through the small abdominal incision, especially in deep-chested dogs.

    Experienced surgeons familiar with the anatomy and the amount of force required to disrupt the SL have adopted many different ways to safely control the rupture of this structure. For inexperienced surgeons, however, the procedure is often daunting and difficult because the ligament is buried within the abdominal viscera and must be identified blindly by palpation. Additionally, in dogs, the SL must be digitally disrupted with considerable force, creating the potential for serious damage to other soft tissue structures, particularly the vascular pedicle of the ovary.

    In veterinary school circles, the process of SL rupture with the index finger is commonly referred to as "strumming" or stretching the ligament. Simply pulling on the SL will rupture it, but the region of disruption is not controlled, and excess tension can cause complete avulsion of the ovarian pedicle and serious bleeding. Using the techniques described in this article, inexperienced surgeons can disrupt the ligament safely with one controlled motion.

    We acknowledge that many successful methods of rupturing the SL exist.3–5 In this article, we describe how we teach two different techniques for performing a "controlled" SL rupture in small animals and explain the rationale for each technique. We have found these techniques particularly useful when teaching novice surgeons. In dogs, we prefer to rupture the SL at its craniodorsal attachment to the abdominal wall because this area is furthest from important vascular structures, which helps reduce the risk of significant hemorrhage. Unlike dogs, cats do not have deep chests and have very little fat around the mesovarium, allowing the SL to be readily distinguished from surrounding tissue; therefore, in cats, the SL can be disrupted sharply close to the ovary. For orientation purposes, the images in this article show the patient with the cranial part of the abdomen to the left, except where noted.

    Surgical Anatomy

    The ovaries, oviducts, and uterine horns are attached to the dorsal abdominal wall by paired double folds of peritoneum called the right and left broad ligaments6 (FIGURE 1A). Within the free cranial border of the mesovarium, between two layers of peritoneum, lies the SL. It is continued caudally by the proper ligament of the ovary, which is a strong fibrous ligament between the uterine horn and ovary. In dogs, the proper ligament has significant strength and can be safely clamped with hemostatic forceps and held firmly to stabilize and retract the ovary and SL. In cats, the proper ligament is fragile, so retraction of this structure must be performed carefully to avoid complete separation of the ovary from the oviduct and uterine horn; hemorrhage; and inadvertent ovarian fragmentation. The SL spans the distance from the ovary to the rib cage and attaches to the middle and dorsal thirds of the last two ribs (FIGURE 1). It must be distinguished from the peritoneal reflections of the mesovarium to the caudal pole of the kidney (see the area below, or dorsal to, the SL in FIGURE 1). In dogs, a considerable amount of fat within the mesovarium conceals the ovarian blood supply and SL. In cats, the mesovarium is not laden with fat, so structures within it are easily observed (FIGURE 2). Because the left kidney is more caudal in the abdominal cavity than the right, the left ovary is usually the most easily retracted and exposed first. For the purposes of this article, the ovarian pedicle refers to both the arterial and venous structures within the mesovarium.

    The ovary is supplied with blood through the ovarian artery, which arises from the aorta caudal to the renal vessels. Within the mesovarium in dogs, the tortuous ovarian veins run close to the ovary, beside the arteries, and drain blood from the ovary and uterus (FIGURE 1A). In cats, the venous drainage is not tortuous and does not branch out as it does in dogs (FIGURE 2). In both species, the right ovarian vein drains directly into the vena cava, and the left ovarian vein drains separately into the left renal vein. Within the canine mesovarium, the indistinct ovarian vasculature also supplies considerable branches to the adipose tissue and capsule of the kidney (FIGURE 3). Blood supply in these branches can be significant, especially during pregnancy and in association with uterine diseases such as neoplasia and pyometritis. Therefore, the portion of the mesovarium attaching to the kidney must be avoided while isolating and disrupting the SL in dogs. Several current veterinary textbooks illustrate SL rupture by depicting the surgeon tearing the "ligament" (mesovarium) that appears to be attached to the kidney.3,5 In cats, ovarian pedicle branches are rarely found extending to the renal capsule, and the SL is distinct, so it is safe to disrupt the SL near the attachment to the ovary (FIGURE 2).

    Intuitive Technical Mistakes During Suspensory Ligament Rupture in Dogs

    In our experience, novice surgeons, who are less familiar with surrounding anatomy, do not want to tear structures they cannot see. Particularly in deep-chested dogs, the SL is often confused with the reflections of the mesovarium attaching to the caudal pole of the kidney during blind palpation. Consequently, novice surgeons attempt to rupture tissue close to the ovary; unfortunately, this is where the blood supply to the ovary and venous branches to the kidney are closest to the SL. The risk of hemorrhage in this vascular area is significantly greater than that in the relatively avascular abdominal wall attachment region (FIGURE 3). In addition, novice surgeons tend to pull up (ventrally) on the proper ligament, which tightens not only the SL but also the mesovarium attachments to the kidney and ovarian pedicle. It then becomes difficult to identify and isolate the SL by palpation. There is also a tendency to put tension on the SL and mesovarium with the index finger pointing in a medial-to-lateral direction (FIGURE 4). Because the medial extension of the mesovarium attaches to the kidney, it is easy to disrupt the tissue to the kidney capsule along with the SL when force is applied this way. Furthermore, the direction of this finger force runs toward the more laterally situated SL attachment and away from the source of the blood supply (the aorta on dorsal midline; FIGURE 4), which may induce more risk of avulsing the ovarian pedicle before SL rupture. We recommend SL rupture with only lateral-to-medial force. Because the SL runs lateral to the kidney as it courses to the dorsal abdominal wall, it is difficult for a novice surgeon to break it using medial-to-lateral force in the least vascular area (at the attachment to the abdominal wall). In our experience, when the procedure described below is performed correctly, the chance of complications involving rib fracture, diaphragmatic tears, or kidney damage is minimal.

    Suspensory Ligament Rupture Technique

    Dogs

    Three tasks are important for safe SL rupture in dogs:

    •  Identify the proper ligament, and clamp it with forceps.
    • Identify the SL at its free cranial border within the mesovarium, and isolate the ligament with the appropriate index finger.
    • Rupture the SL in a controlled fashion from a lateral-to-medial direction as close as possible to the SL attachment to the abdominal wall.

    Identify the proper ligament, and clamp it with forceps. Once the uterus is identified, follow one of the uterine horns cranially until the ovary can be palpated (FIGURE 5). In deep-chested dogs, the ovary may not be visible, but the tough proper ligament to the ovary can be isolated and clamped with hemostatic forceps.

    Identify the SL at its free cranial border within the mesovarium, and isolate it with the appropriate index finger. Regardless of whether the surgeon is right- or left-handed, or on which side of the patient the surgeon is standing, the left index finger is used to disrupt the right SL (FIGURE 6 A and FIGURE 6 B), and the right index finger is used to disrupt the left SL (FIGURE 6C). The surgeon's body should be oriented toward the cranial aspect of the animal during SL rupture. Using the hemostatic forceps on the proper ligament as a handle, pull the ovary in a caudomedial direction (not too much ventrally), which should create tension directly on the SL alone (not the medial attachments of the mesovarium to the kidney or the ovarian pedicle). Maintain this tension throughout the remaining portion of the SL rupture maneuver.

    Rupture the SL in a controlled fashion in a lateral-to-medial direction as close as possible to the SL attachment to the abdominal wall. With the palm of the hand facing medially, allow the correct index finger to course along the lateral aspect of the taut SL as far cranially as possible until the attachment fans out to the abdominal wall. While the other hand holds the hemostatic forceps and maintains tension on the ligament, use only the index fingertip to avulse the ligament from its attachment to the abdominal wall (pull only as hard as necessary on the hemostatic forceps to keep the index finger firmly positioned on the SL). Sudden rupture is accomplished by thrusting the index finger held on the SL in a craniomedial direction (FIGURE 7A). (Click here for a suggested practice exercise using suture in place of the SL.) Do not put additional tension on the hemostatic forceps while pushing the index finger, or the SL will break indiscriminately along its course rather than just at the wall attachment.

    When the technique is performed correctly, the SL either "pops" and ruptures completely or stretches out but remains partially intact. Either outcome is acceptable provided that the ovary and pedicle are adequately exposed. If the ligament is stretched, gentle caudal tension on the hemostatic forceps while the index finger is depressed dorsally on the middle of the SL will break down any remaining SL attachments. When performed correctly, the SL consistently ruptures at its weakest point—its fanned out attachment—well away from important vascular structures found more caudally (FIGURE 7B). The ovarian pedicle is double ligated using a proper three-clamp hemostatic technique. Repeat the procedure on the opposite side.

    Cats

    SL rupture in cats is more straightforward because the cat's cranial abdomen is shallower than that of deep-chested dogs, and the SL and ovarian pedicle can be readily seen within the mesovarium (FIGURE 2). The ovarian pedicle and proper ligament to the ovary are considerably more fragile in cats than in dogs, so traction on these structures for SL rupture (as in dogs) is more dangerous. Therefore, we recommend sharp rather than blunt division of the SL in cats. After completing the celiotomy approach and grasping one of the uterine horns, carefully identify the ovary and SL. While gently pulling the uterus caudal and up (or more ventral), sharply incise the ligament away from ovarian tissue, and retract the ovary from the abdominal cavity to expose the ovarian pedicle (FIGURE 8). Any avascular portion of the mesovarium cranial to the ovary can be sharply broken down if additional exposure is necessary. Securely double ligate the ovarian pedicle using a three-clamp technique. Repeat the procedure on the opposite side.

    Downloadable PDF

    Dr. Smeak discloses that he has received financial benefits from Covidien.

    1. Johnson AL, Greenfield CL, Klippert L, et al. Frequency of procedure and proficiency expected of new veterinary school graduates with regard to small animal surgical procedures in private practice. JAVMA 1993;202:1068-1071.

    2. Stone EA. Reproductive system. In: Slatter D, ed. Textbook of Small Animal Surgery. St. Louis: Saunders; 2003:1495-1498.

    3. Fingland RB. Ovariohysterectomy. In: Bojrab MJ, Ellison GW, Slocum B, eds. Current Techniques in Small Animal Surgery. Baltimore: Williams and Wilkins; 1998:489-492.

    4. Sicard GK, Fingland RB. Surgery of the ovaries and uterus. In: Birchard SJ, ed. Saunders Manual of Small Animal Practice. St. Louis: Saunders; 2006:992-998.

    5. Fossum TW. Surgery of the reproductive and genital systems. In: Small Animal Surgery. St. Louis: Mosby; 2002:616-617.

    6. Evans HE, Christenson GC. Miller's Anatomy of the Dog. Philadelphia: WB Saunders; 1981.

    References »

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