Lower urinary tract injury during gynecologic surgery is relatively uncommon. Bladder injuries are the most frequent urologic injury inadvertently caused by a surgeon. Bladder injuries usually are recognized and repaired immediately, and potential complications are typically minor. However, ureteral injuries typically are not recognized immediately and have the potential to be life-threatening or to result in permanent kidney damage or removal of a kidney. (1)

Anatomy of the Ureters

The ureters are a pair of tubes that carry urine away from the kidneys to the bladder. In the bladder, the urine is stored and then emptied by urination. The adult ureter is a delicate structure, about the width of a pencil, and roughly 30 cm in length.

Ureteral Injuries

Ureteral injuries are a potential complication of any open or endoscopic pelvic operation. Gynecologic surgery accounts for more than 50 percent of all ureteral injuries resulting from an operation, with the remaining occurring during colorectal, general, vascular and urologic surgery. (2-4) The ureter is injured in roughly 0.5 to 2 percent of all hysterectomies and routine gynecologic pelvic operations and in 10 percent (range, 5 to 30 percent) of radical hysterectomies. (4-6) Ureteral complications from radical hysterectomy have declined over the years because of improved patient selection, limiting of surgery to mostly low-stage disease, decreased use of preoperative radiation and modifications in surgical technique that limit extreme skeletonization of the ureter. (6) Of ureteral injuries from gynecologic surgery, roughly 50 percent are from radical hysterectomy, 40 percent are from abdominal hysterectomy and less than 5 percent result from vaginal hysterectomy. (1) All gynecologic ureteral injuries occur to the distal one third of the ureter (or in other words, the segment of ureter closest to bladder and in the pelvis).
 
The ureter can be injured during any anterior vaginal wall surgery that extends to the bladder neck (such as vaginal hysterectomy, bladder neck suspension surgery, anterior repair of the vaginal wall, repair of an enterocele [hernia] and neovagina construction). Repair of high-grade pelvic prolapse (that is, grade 4 cystocele [hernia of the bladder] or total uterine prolapse) pose a particular risk for ureteral injury. The majority of ureteral injuries here are during vaginal vault reconstruction or vaginal cuff closure, where sutures can ligate (be tied to) the ureter or kink the ureter by displacing it. Prolapse patients can have extremely dilated and thin ureters that can be enclosed in the prolapse and, thus, be predisposed to potential ureteral injury. (7) Similarly, in pregnancy, the ureters are dilated, exposure is difficult and the risks are increased. Other gynecological procedures that can result in ureteral injury are abdominal oophorectomy (removal of an ovary), pelvic mass resection, removal of a fallopian tube, caesarian section, adnexectomy (removal of one of the uterine tubes and an ovary), extended pelvic lymphadenectomy (removal of lymph nodes) and laparoscopy (a minimally invasive method used to examine the interior of the body or to perform surgery). (8-10)

Risk Factors and Prevention of Ureteral Injury

Prevention

The most reliable way for surgeons to avoid ureteral injury is to clearly identify the ureter throughout the region of the body that will undergo the operation.
 
For pelvic operations expected to be difficult, or for patients with large pelvic masses, pelvic inflammatory disease, prior pelvic surgery or prior irradiation, the use of preoperative ureteral radiographic imaging by intravenous urography (IVU) or computed tomography (CT) has been widely advocated. However, placement of a stent (a short, narrow tube) in the ureter is not recommended on a routine basis. In fact, most ureteral injuries occur during technically straightforward hysterectomies for minimal disease. (2, 10)
 
In most cases, ureteral identification is not difficult and, thus, preoperative stents are unnecessary. However, stent placement clearly helps identify a ureteral injury when it does occur. Furthermore, if surgical removal is difficult, stents can be placed as part of the operation, with the use of a cystoscope (a type of endoscope, or fiber-optic instrument) or through a small surgical incision of the bladder. When a pelvic tumor is large or ureteral anatomy is distorted on preoperative imaging, preoperative stents may increase the ability to examine the ureters by touch, minimize need for ureteral removal and minimize ureteral kinking by adjacent suturing. (11)
 
The initial point in preventing ureteral injury is acknowledging and recognizing the risk for injury. Regardless of the ureteral position on imaging, it is important to recognize the potential hazards and to identify the ureters despite the presence of disease and through their pelvic course. In general, generous surgical exposure, meticulous surgical technique and visual ureteral identification all are more useful than preoperative body imaging or ureteral stenting.

Risk Factors

Most ureteral injuries (80 to 90 percent) occur in the part of the ureter in the pelvis, the segment of ureter closest to the bladder. In vaginal hysterectomy, the primary risk point is the clamping and ligation (tying) of the cardinal ligaments. As the cervix is pulled down through the vaginal opening, the bladder and ureters follow. Therefore, if the incision is high on the cervix, the bladder/ureters can be incorporated in the incision. Ureteral obstruction on ligation of the cardinal ligaments is typically due to ureteral kinking from a suture in close proximity, rather than a ligation injury. (12)
 
Abnormalities of the ureter and/or surrounding tissues can alter the ureter pelvic anatomy and displace the ureter into an abnormal location, and in so doing substantially increase the risk for ureteral injury. Such anatomic abnormalities usually are found with endometriosis or pelvic tumors. Congenital abnormalities, such as ureteral duplication, a wide ureter, ectopic ureter (when the ureter drains to an abnormally located opening, like the vagina) or ectopic kidney (a kidney that lies in an abnormal position or location) make injury during surgery more likely. The ureter also is predisposed to injury by extreme lateral displacement of the cervix, mass adherence to the pelvic peritoneum, a fibroid uterus (tumor consisting of muscle tissue) or other tumors of the broad ligament, abscess or mass in the broad ligament base, or cervical cancer.
 
However, the majority of reported ureteral injuries have occurred in patients with no identifiable risk factors. In fact, more than 75 percent of ureteral injuries due to gynecologic surgeries occur during procedures that surgeons describe as uncomplicated and routine and where pelvic anatomy is normal. (10) Hemorrhage (extensive bleeding) during the operation is a clear and main risk factor for ureteral injury. Sudden hemorrhage should never be treated with blind cautery (searing of tissue) or suturing, but rather direct pressure, sharp dissection and exposure of the bleeding vessels followed by accurate and precise suturing. (2,3,10)
 
As previously stated, abdominal hysterectomy is the most common source of ureteral injury inadvertently caused by a surgeon. Here, the potential for ureteral injury is greatest during the ligation and division of the uterine arteries, followed by division of the ovarian vessels and infundibulopelvic ligament (a ligament of the ovary). In radical hysterectomy, the ureter can be skeletonized when removing an adjacent tumor, and this can result in a lack of blood supply and delayed death of tissue. Radical hysterectomy also may require en-bloc resection (removal as a unit) of a ureteral segment (in order to achieve a tumor-free margin). Prior irradiation can compromise ureteral blood supply, make wounds heal poorly and increase the risk of ureter injury during pelvic surgery (after hysterectomy by three to fourfold). Fistulas (abnormal passages draining urine) from the radiated ureter are very difficult to repair and typically require two or more operations. (13) Previous episodes of endometriosis or pelvic inflammatory disease can lead to dense ureteral adherence and so increase the chances for injury during surgery. Cancers can directly invade and can fix the ureter or distort its course. Masses in the ovaries and fallopian tubes also can distort the infundibulopelvic ligament and displace the ureter. Severe pelvic prolapse also can increase the risk of ureteral injury. Infected or inflamed tissues are other important contributing factors for ureteral injury. (14)

Diagnosis

During the Operation

If injury to the ureter is suspected during the operation, the ureter must be meticulously examined in the area of interest. Like others, we have found that direct exploration and visual inspection are the most common and accurate methods for diagnosis. If no obvious urine leak is noted at the suspected injury site, to help identify the ureteral injury, indigo carmine can be injected into the ureteral opening (after the bladder has been opened) or injected directly into the ureter or a portion of the kidney. The injection of indigo carmine into a vein coupled with Lasix diuretic (a substance that increases the excretion of urine), which colors the urine blue, is also helpful. The blue-tinged urine helps confirm injury. (15,16)
 
Even without urine being forced out, a ureter with a bruised appearance can have significant trauma from either a crush or ischemic injury (an injury resulting from deficient blood supply). Ways to determine whether a ureter has lost blood supply are to note wall discoloration, absence of refill of the capillaries, or most reliably, by making an incision in the ureter and inspecting the ureteral edge for bleeding. A ureter that visibly can contract, unfortunately, is not a clear indication of normal ureteral function or of adequate blood supply. Some have advocated the use of intravenous fluorescein and a Wood’s lamp to assess whether the ureter has an adequate blood supply (15) 

Postoperative

Intravenous urography (dye and X-ray study of the kidneys and ureter) findings suggestive of ureteral injury are delayed visualization or the inability to visualize the involved kidney, hydronephrosis (distension of both kidneys because urine is unable to drain from them) , or incomplete visualization of the entire ureter. Retrograde urography is typically the most sensitive radiographic method to evaluate the integrity of the ureter, and to determine if it has been damaged. Ultrasound or CT can identify a hematoma (clotted blood), a cyst containing urine or hydronephrosis, all suggestive of ureteral injury.

Signs and Symptoms

The findings associated with a missed ureteral injury are generally nonspecific. Suggestive of urinary leak are a prolonged bowl obstruction, persistent pain in the abdomen or in the side between the ribs and the hip, an abdominal mass that can be felt, an elevation in blood urea nitrogen, fever/body-wide response to serious infection, an increase in white blood cells, or prolonged and persistent drainage from the vagina or from the operative drains/drain sites. Frequently, ureteral injury is not discovered until an obvious fistula (abnormal passage) occurs. 

Types of Injury

The common types of pelvic ureteral injuries caused by surgery – in descending order of frequency – are ligation, kinking by suture, division, partial laceration, crush and loss of blood supply (leading to delayed death of tissue and narrowing of the ureter). (17).

Management

The method of ureteral repair is determined by many factors, including the location and length of ureteral injury, the time of diagnosis (during the operation, early postoperative or delayed), the type of injury and the presence of associated medical or surgical illnesses.
 
Clearly, the optimal time for repair of a ureteral injury is during the operation, when it initially occurs. At the time of injury, the tissues are typically in their best condition, where the options and likelihood for success are greatest. Immediate recognition and repair allow for better results and fewer complications than in a delayed fashion.
 
Unfortunately, most ureteral injuries from gynecologic surgery (more than 80 percent) are discovered in a delayed fashion. (1) Injuries that are detected after an operation tend to be more complex, require more complex repairs and multiple procedures, and have more complications than those detected and repaired during the operation. (18,19)

Laparoscopic Injury

Ureteral injuries during laparoscopic gynecologic surgeries typically occur during laser ablative endometriosis surgery or laparoscopic-assisted vaginal hysterectomy (LAVH). (20) There are also reports of ureteral injury during laparoscopic tubal ligation, adnexectomy (removal of one of the uterine tubes and an ovary) and laparoscopic uterosacral ligament ablation. Most LAVH ureteral injuries occur near the cardinal and uterosacral ligaments and are caused by either thermal-electrocautery or sharp dissection. (20) There are also reports of ureteral injury caused by CO2 laser, endoscopic linear stapler and loop ligature. (21,22) Ureteral injuries, ranging from small partial tear to complete ureteral tearing away, typically occur in patients with a history of pelvic irradiation or prior extensive pelvic surgery. Overall, complications often are related to surgical experience. (23)

As with open surgery, preoperative intravenous urography or ureteral stent placement are of limited routine value in preventing ureteral injury. (24) For technically difficult cases, ureteral catheters in laparoscopy may enhance identification and make dissection easier. Lighted ureteral catheters are also available and may help in ureteral identification. (21,22)

Partial ureteral lacerations or thermal injuries that are diagnosed during the operation can be managed by endoscopic placement of a ureteral stent (for four to six weeks). Laparoscopic suturing of the lacerated ureter also has been performed successfully. When the ureter has been cut completely, an immediate, open surgical approach is typically needed. (9) If the surgeon is especially skilled and the injury site allows, the ureter can be repaired through the laparoscope. However, most ureteral injuries are diagnosed in a delayed fashion, typically several days after the operation. (20, 21)

Delayed Ureteral Complications

When a ureteral injury is diagnosed and repaired at the initial presentation/exploration, rarely is there a high degree of sickness. However, when diagnosis is delayed, sickness including body-wide response to serious infection, loss of kidney function and possible death can occur in up to 50 percent of patients. Rates for surgical removal of the kidney resulting from delayed diagnosis, overall, are seven times as common as when the ureter injury is diagnosed promptly (during surgery). Urine leakage also can cause abscess and scarring of the ureter, leading to obstruction and formation of abnormal passages. (25)

Urinary Discharge

Initially, a ureter that is cut produces no symptoms until a cyst collecting urine causes abdominal swelling, bowel obstruction, infection, fever or low back, side or abdominal pain and/or signs in the membrane that lines the abdominal cavity. Persistent blood in the urine, increase in white blood cells and/or urinary (fluid) leakage from the vagina are other reliable signs of injury. Absorption of the urine by the abdominal membrane will often cause a rise in the serum urea nitrogen. Such injuries have been managed successfully by a variety of methods, from ureteral stent placement for minor injuries to open surgical repairs. When the patient is medically unstable, has a body-wide response to infection or the injury is not detected for more than two to three weeks, the patient typically requires proximal urinary diversion (that is, a tube leading from the kidney to the outside of the body and, if technically possible, ureteral stent placement), as well as drain placement into the urine-containing cyst. The discharged urine also may cause fibrosis (development of fibrous tissue) behind the abdominal membrane severe enough to cause ureteral obstruction, particularly if the area is not drained properly. At two to three weeks after surgery, re-exploration is typically difficult and fraught with danger because of inflammation, fibrosis, adhesions, blood clotting and distorted anatomy. Definitive repair is performed in a delayed/staged fashion. (1,26)

Fistulas

Fistulas (abnormal passages – mainly ureterovaginal) are rare after ureteral repair. They usually develop when the ureteral injury is undiagnosed during the operation, and the ureter undergoes delayed tissue death and/or narrowing (obstruction). Other factors that contribute to fistula formation are infection (abscess, peritonitis), inflammation, foreign body and tumor formation. (27) A history of prior pelvic irradiation (that is, for cervical cancer) is another independent risk factor, increasing the risk for fistula formation after hysterectomy by three to fourfold and complicating the difficulty of fistula repair. (10, 13,20) Ureteral fistulas usually do not require an open operation and typically close spontaneously with proper drainage and ureteral stenting. (27,28)

Stricture

Stricture (narrowing) develops when a ureter with deficient blood supply, often from a certain type dissection, heals by scar tissue. Side or abdominal pain and urinary tract infection/pyelonephritis (kidney inflammation) are commonly seen. Ureteral strictures that are diagnosed early (within six to12 weeks), are in the portion away from the kidney and are relatively short in length (less than 2 cm) can be managed successfully (in about 50 to 80 percent of cases) by balloon dilatation or endoscopic incision and stenting for six weeks. For endoscopic failures, an open surgical repair is necessary. When the stricture is discovered late, particularly dense or long, or radiation induced, open segmental removal and repair are usually necessary. (27,29)

Bladder Injuries

When a bladder injury is discovered during pelvic surgery, it is wise also to investigate the possibility of an accompanying ureteral injury. Direct inspection of the surgically exposed ureter or the ureter after indigo carmine administration is often sufficient. If the patient had received prior pelvic irradiation, the bladder repair should be covered with omentum or peritoneum (two types of abdominal membrane), if available, to prevent possible formation of a fistula. Bladder rest by Foley catheter is typically employed for seven to 14 days. A tube is generally unnecessary for female bladder trauma unless there is a considerable amount of blood in the urine that could obstruct the catheter. A suction drain is placed until the drainage is minimal. If drainage output remains high, the drainage fluid should be sent to the lab to examine the concentration of the compound creatinine. Creatinine levels greater then serum indicate a urine leak, whereas levels equal to serum indicate peritoneal or lymphatic fluid. Persistent urinary leakage typically resolves with an additional two to four weeks of bladder drainage. (28)

Abdominal Hysterectomy

In gynecologic surgery, bladder injury most commonly occurs during abdominal hysterectomy. The bladder can be injured at four specific sites. If a bladder injury is noted at this time, it usually can be easily managed by a two- or three-layer closure with absorbable suture and Foley catheter bladder drainage. Retrograde bladder filling with blue-colored saline again makes bladder injury diagnosis easier.

Vaginal Hysterectomy

Most bladder injuries during vaginal hysterectomy are in a specific area of the bladder base. (30) For such bladder injuries, cystoscopy is often helpful to identify the location of the injury. If there is any suspicion of an accompanying ureteral injury, indigo carmine should be injected through the veins and the ureteral openings observed for blue dye. Once ureteral injury is ruled out, the bladder injury can be repaired in two or three layers. The adequacy (water-tightness) of the bladder closure can be tested by retrograde filling of the bladder with saline. A Foley catheter is typically left in place for seven to 14 days. After the bladder laceration has been repaired, the vaginal hysterectomy can be completed and/or anterior surgical repair of the vaginal wall performed.

Laparoscopy

When injured, the bladder is usually penetrated by, and on initial placement of, the Veress needle or trocar (a surgical instrument). Trocar injuries are typically to the bladder dome and have an entry and exit wound. To avoid bladder injuries, it is essential that the bladder is decompressed by a Foley catheter at the beginning of the case. The position of the bladder should be assessed on initial examination with the laparoscope. All secondary trocars should be placed under direct visualization. Bladder injuries occur most often with midline and lower abdominal trocar placement. A full bladder or one with distorted anatomy from previous pelvic surgery, endometriosis or adhesions is more likely to be injured laparoscopically. (21)

During the operation, the diagnosis of bladder injury is suggested by the presence of gas filling up the Foley bag or visibly bloody urine in the Foley bag. Other signs of injury are urinary/fluid drainage from a secondary trocar site incision, or fluid pooling in the abdomen/pelvis. If a bladder injury is suspected, the bladder should be filled with methylene blue-colored saline. The forcing out of fluid/dye indicates a bladder injury inside the abdominal membrane. If there is no fluid forced out and a bladder injury outside the abdominal membrane is suspected, a cystogram (X-ray of the bladder after injection of contrast medium) should be performed. Injuries outside the abdominal membrane are managed conservatively through prolonged Foley drainage. Delayed diagnosis of bladder injury also is done by cystography. Irritation of the abdominal membrane that persists more 12 hours after laparoscopy also should raise suspicion of an undiagnosed bladder injury. (9,21,24)

Veress needle injuries and other small injuries to the bladder can be successfully managed conservatively by catheter drainage for seven to 14 days followed by cystography. Large bladder injuries, such as from 5 or 10 mm trocar or surgical dissection, often require suturing the injuries closed (either laparoscopically or by open repair) and prolonged catheter drainage. A bladder injury recognized by laser or electrocautery should be closely evaluated and typically managed with catheter drainage for five to 10 days. Sharp dissection, electrocautery and laser bladder injuries also have been reported during laparoscopic-assisted vaginal hysterectomy, adnexectomy (removal of one of the uterine tubes and an ovary), diagnostic laparoscopy and endometriosis surgery. (9,21)

Delayed Bladder Injury/Diagnosis

Cystography with a post-drainage X-ray will enable the surgeon to assess injury inside and/or outside the abdominal membrane. Injuries inside the abdominal membrane require surgical closure and drainage, whereas injuries outside the abdominal membrane can be successfully managed through prolonged Foley catheter drainage. Decreased urine output, absent or defective urine excretion, an excess of urine, elevated blood urea nitrogen, the presence of blood in the urine, bruising and abdominal swelling suggest a bladder injury has been missed.

Undiagnosed injuries to the bladder that occur during surgery typically become evident days to weeks after surgery. In patients with previous pelvic irradiation, fistulas can occur months to even years after hysterectomy. Typical delayed bladder complications are various forms of fistulas. For further details on bladder fistulas, see two of the referenced papers below by Saidi et al. (21) and Mandal et al. (27).

References

  1. Selzman AA, Spirnak JP. Iatrogenic ureteral injuries: A 20-year experience in treating 165 injuries. J Urol 155:878-881, 1996.
  2. Higgins CC. Ureteral injuries during surgery. A review of 87 cases. JAMA 199:82, 1967.
  3. Neuman M, Eidelman A, Langer R, Golan A, BukovskyI, Caspi E. Iatrogenic injuries to the ureter during gynecologic and obstetric operations. Surg Gynecol Obstet 173:268, 1991.
  4. Dowling RA, Corriere JN Jr., Sandler CM. Iatrogenic ureteral injury. J Urol 135:912, 1986.
  5. Fry DE, Milholen L, Harbrecht PJ. Iatrogenic ureteral injury. Arch Surg 118: 454, 1983.
  6. Underwood PB Jr., Wilson WC, Kreutner A, Miller MC III, Murphy E. Radical hysterectomy: A critical review of twenty-two years experience. Amer J Obstet Gynecol . 134:889, 1979.
  7. Kontogeorgos L, Vassiloppoulos P, Tentes A. Bilateral severe hydroureteronephrosis due to uterine prolapse. Br J Urol 57(3):360-1, 1985.
  8. Eisenkop SM, Richman R, Platt LD, Paul RH. Urinary tract injury during cesarean section. Obstet Gynecol 60:591, 1982.
  9. Grainger DA, Soderstrom RM, Schiff SF, Glickman MG, DeCherney AH, Diamond MP. Ureteral injuries at laparoscopy: Insights into diagnosis, management, and prevention. Obstet Gynecol 75: 839, 1990
  10. Symmonds RE. Ureteral injuries associated with gynecologic surgery: Prevention and management. Clin Obstet Gynecol 19: 623-644, 1967.
  11. Rodriguez L, Payne CK. Management of Urinary Fistulas. In: Taneja SS, Smith RB, Erlich RM (eds.). Complications in Urologic Surgery. 3rd ed. Philadelphia: WB Saunders; 2001:186-205.
  12. Williams TJ. Urologic Injuries. In: Wynn RM (ed.). Obstetrics and Gynecology Annual. New York: Appleton-Century-Crofts; 1975:327-368.
  13. Green TH, Meigs JV, Ulfelder H, Curtin RR. Urologic complications of radical Wertheim hysterectomy: Incidence, etiology, management, and prevention. Obstet Gynecol 20:293, 1962.
  14. Talbert LM, Palumbo L, Shingleton H et al. Urologic complications of radical hysterectomy for carcinoma of the cervix. South Med J 58:11, 1965.
  15. Presti JC, Carroll Pr, McAninch JW. Ureteral and renal pelvic injuries from external trauma: Diagnosis and management. J Trauma 29 :370, 1989.
  16. Campbell EW, Filderman PS, Jacobs SC. Ureteral in jury due to blunt and penetrating trauma. Urology 40:216, 1992
  17. Higgins CC. Ureteral injuries during surgery: A Review of 87 cases. JAMA 199:118,1967.
  18. Zinman LM, Libertino JA, Roth RA. Management of operative ureteral injury. Urology 12:290, 1978.
  19. Fry DE, Milholen L, Harbrecht PJ. Iatrogenic ureteral injury: Options in management. Arch Surg 118:454, 1983.
  20. Tamussino KF, Lang PFJ, Breinl E. Ureteral complications with operative gynecologic laparoscopy. Am J Obstet Gynecol 178:967-70, 1998.
  21. Saidi MH, Sadler RK, Vancaillie TG, Akright BD, Farhart, SA, White AJ. Diagnosis and management of serious urinary complications after major operative laparoscopy. Obstet Gynecol 87:272-6, 1996.
  22. Woodland MB . Ureter injury during laparoscopic-assisted vaginal hysterectomy with the endoscopic linear stapler. Am J Obstet Gynecol 167:756-757, 1992.
  23. See WA, Cooper CS, Fisher RJ. Predictors of laparoscopic complications after formal training in laparoscopic surgery. JAMA 270:2689-92, 1993.
  24. Daly JW, Higgins KA. Injury to the ureter during gynecologic surgical procedures. Surg Gynecol Obstet 167:19-22, 1988.
  25. McGinty DM, Mendez R. Traumatic ureteral injuries with delayed recognition. Urology 19 :115, 1977.
  26. Guerriero WG. Injuries to the ureter: Part 1, mechanisms, prevention and diagnosis. AUA Update 2(22):1-7, 1983.
  27. Mandal AK, Sharma SK , Vaidyanathan S, Doswani AK . Ureterovaginal fistula: Summary of 18 years experience. Br J Urol 65:453, 1993
  28. Williams RD. Urologic complications of pelvic surgery. In: Jewett MAS (ed.). Urologic Complications of Pelvic Surgery and Radiotherapy . Isis Medical Media, Oxford ; 1995:1-22.
  29. Meirow D, Moriel EZ, Zilberman M, Farkas A. Evaluation and treatment of iatrogenic ureteral injuries during obstetric and gynecologic operations for nonmalignant conditions. J Amer Col Surg 178:144, 1994.