The main purpose of this article is to describe the anatomy of twisted uterus in cattle, assess the risk factors involved in pre-disposing cattle to this disease, assess and suggest reasons for patterns observed in the prevalence and incidence of the disease; as well as outlining the most common ways of correcting torsions.
What is Uterine Torsion?
By its more commonly known name, ‘twisted uterus’, this disease is fairly self-explanatory in terms of what the main problematic components are. In the UK, dairy cattle are the species with the highest incidence of twisted uterus cases; however, globally this incidence is massively dwarfed by the number of buffalo cases treated for uterine torsion. A better understanding of what uterine torsion is and exactly which anatomical components are involved can help to explain the difference between cattle and buffalo uterine torsion cases.
Animals that are part of the family Bovinae, including cattle, bison and buffalo, all share a similar ‘design flaw’ when it comes to the structure of their female reproductive organs. The uterus (more specifically, the uterine horns) are held in place by broad ligaments which provide dorsolateral support (i.e. they keep the uterus in a horizontal placement, up towards the spine of the animal). These ligaments are attached to the ventral side of the uterus (i.e. attaching to the uterus on the under-side).
In non-pregnant animals, this is a perfectly stable structure as the uterus is harbouring no extra weight and is situated in a fairly non-mobile position within the body cavity. However in pregnant cattle, as gestation advances, uterine contents grow, increasing the weight and size of the uterus; the broad ligaments do not extend proportionately, leading to instability of the uterus. Furthermore, the gravid (pregnant) uterus is positioned beyond the relatively stable area of attachment – instead, resting on the abdominal floor and being supported by the rumen, viscera and abdominal wall.
When instable, as is the case when the cow is in late stages of gestation, the uterus is at its most susceptible to being twisted. As a result of aggression from another cow, slipping over, turning quickly round corners, standing up and sitting down overly frequently or simply the myometrial contractions of the womb at the onset of parturition, the uterus can become ‘twisted’. What this actually means is that at a point along the birth canal, the uterus (and possibly some vaginal wall and cervix) has rotated around a point, to create a twist in the birth canal – this essentially halts any stages of labor from progressing.
The twist can be anywhere between a 45 degree angle up to 360 degrees. The larger the degree of twist, the more difficult the correction of the twist is. The twist direction can be anti-clockwise (left) or clockwise (right). Illustrated by the images below, where the red circle represents the uterus and the black dotted line represents the normal horizontal plane of the uterus.
If the twist was 360 degrees, the birth canal becomes almost impossible to fit through. The image below shows the normal birth canal (left) and the birth canal with a 360 degree twist, the blue lines representing the birth canal walls.
The foetus and its membranes also rotate with the uterus, meaning that there is a compression of blood supply to the foetus in the womb – death is often the case if intervention is not fairly prompt.
When the uterus twists, the broad ligaments also change positioning. This makes it possible to diagnose uterine torsion by rectal examination, palpating the broad ligaments to determine their position.
The point of torsion can be at several points along the birth canal. From the perspective of the calf, it can be before the cervix (pre-cervical torsion) or after the cervix (post-cervical torsion). Post cervical torsions are often more easier to diagnose visibly as more of the vaginal wall tissue and vulval lips are involved – showing signs of tension and a characteristic ‘corkscrew’ effect in the tissue of the vaginal wall, getting tighter towards the point of torsion.
The direction of the twist can (and must be) identified by the twisting in the vaginal wall. If the vaginal wall is corkscrewing to the left, then the uterus has twisted to the left, when viewing the cow from behind. Correction would therefore involve twisting the uterus to the right to oppose the initial twist.
Uterine torsion essentially creates a blockage in the birth canal. In twists greater than 90 degrees, it is rare that the water bag can pass through, meaning that often, first stage labor is noted but the progression to stage 2 is extremely slow or in fact non-existent. Torsions occur just before stage 1, during stage 1 or at initiation of stage 2 of labor.
Although this is not a problem in non-pregnant cows, as mentioned before the gravid uterus of pregnant cattle is carrying significantly more weight. When the hind quarters are raised in the air as shown by the illustration above, the gravid uterus is essentially hanging in the abdominal cavity, pushing forwards on the abdominal wall and almost hanging with a vertical axis (instead of a longitudinal axis), which makes it more likely that the uterus will twist due to the vertical angle at which the uterus is hanging, especially if a slip of fall occurs as the cow is getting up. The red line above represents the axis that the uterus will have, compared to the yellow line which is the axis the uterus should have when the cow is lying flat (which is most stable) and the blue circle shows the area in which the uterus is suspended within. So instead of being flat and stable, if the cow is frequently getting up and lying down, there is an increased chance of the uterus twisting. Alternating between lying and standing is a common behaviour for a cow that is about to calve so essentially at this time the cow is at the most risk. In light of this it is of vital importance to ensure that the environment of the cow at this point is safe – i.e. the chances of the cow slipping, falling or being pushed by other cows, is minimal.
Uterine torsion occurs most commonly in stage 1 of labor or onset of stage 2 of labor. Often it is recognised by failure of the cow/heifer to progress in calving. Due to the obstruction in the birth canal caused by the twist, it is unlikely that the any fluids are expelled and palpation of the calf is more difficult. Cows will often hold out their tail/tailhead and act more restless. The vulval lips are sometimes tight or skewed in cases of strong twists and the vaginal walls are much drier than they should be at stage 1/2 of labor.
It is therefore important to recognise and take note of when a cow is entering into first stage of labor. The most difficult and severe cases of uterine torsion are those that have been left too long before seeking veterinary assistance – in other words, the stockman has not recognised the delay in progression. Although delays can be common and not disease related, the time taken to check the dilation of the cervix or check for a twisted uterus is much less than the time, effort and cost of a severe uterine torsion case.
Pertaining to the original statement of buffalo being more susceptible than cows now, using the information given so far, this can be explained. Buffalo nowadays have a very weak musculature of broad ligaments, as well as an extremely ‘deep’ abdomen compared to cows – therefore, combining these predisposing anatomical factors (i.e. the weak musculature, deep abdominal cavity and the poor bovinae broad ligament structure) this makes buffalo the most susceptible to uterine torsion compared to any other species.
Clinical Signs of Uterine Torsion
Although recognising the clinical signs of uterine torsion can help to detect cases of the disease, generally speaking, the stockperson’s knowledge of that animal is of more use in aiding detection. Knowing your cattle well is the best tool for early detection – nevertheless, looking out for clinical signs can be helpful…
· Non-progression of labor
· Tight, unlubricated vaginal cavity
· Conical, corkscrew appearance of vaginal lining
· Twisted, tight or skewed vulval lips
· Inability to see or feel calf inside the birth canal
· Restless or stressed behaviour
· Increased heart rate
· Increased breathing rate
· Increased levels of progesterone compared to control animal
· Decreased levels of estradiol-17 (type of oestrogen) compared to control animal
· Fever presented in around 1 in 5 cases
· In cases of torsion in in mid-gestation, colicky signs along with signs of impending parturition are presented – if left unattended then dullness, anorexia and toxaemia may occur.
What can research and studies tell us about the patterns of uterine torsion?
Research and studies into the risk factors involved in uterine torsion do exist, however, the application of their conclusions have not been insightful in many situations; this is most probably due to the large range of factors which could affect or cause the uterus of a cow to twist. It may be that many small predisposing factors add-up to cause the torsion, or one single direct cause is the problem. Either way, the causal factors are still not fully understood fully and are therefore still under speculation.
One common pattern found in most studies that most of the cases involve post-cervical torsions (i.e. the point of rotation occurs between the cervix and the vulva, not the cervix and the womb). This would explain why most cases of torsion can be identified by the conical corkscrew appearance of the vaginal lining; if the vaginal wall is involved in the torsion, the lining of the vagina is tighter and so more vaginal tissue is involved compared with pre-cervical torsions.
Another common observation is that the direction of the twist is most commonly seen to the left (anticlockwise). This is not likely to be because of any kind of behavioural or management factor (as all cattle behaviours and managements systems are generally different) and therefore it seems it could be an internal factor which could be important. We know that the pregnant horn (9 times out of 10) will rotate over the non-pregnant horn. This means that, in most cases of uterine torsion, the right horn is pregnant and is rotating over the left horn (non-pregnant). If there are anatomical differences in the horn-ligament structures between right and left horns, this could play a part.
In all studies into uterine torsion, the Brown Swiss breed of cattle has been noted to be the most susceptible. Dairy cattle are generally more susceptible than beef cattle. Friesian-Holstein being at most risk behind Brown Swiss – although, this statistic may be skewed by the shear amount of Friesian-Holstein herds compared to other breeds, meaning there is more data available for these herds and therefore it makes sense that we would see more cases of uterine torsion dystocia in these herds.
Specific case studies, the results and their implications in terms of risk factors…
164 cases of uterine torsion in North America:
Of the cases analysed, 90% (178/194) of the calves born to uterine torsion in dams had a higher than average birth weight – this would strongly suggest that large calves increase the risk of uterine torsion.
Maintaining a steady feed intake for cows during the last 6 weeks of pregnancy is important as this is the time in which the calf growth rate is the highest. An increased feed intake at this stage may lead to excessive calf weight gain and consequently increase the chances of uterine torsion during parturition.
63% of cases were male calves – it is highly improbable that this result means that male calves increase the risk of torsion because of the gender of the calf; instead, it is likely that because males are on average bigger and heavier calves, they increase the instability of the gravid uterus during gestation.
Although having large calves may seem a good idea to some stockmen, the future implications may outweigh these benefits. A larger calf increases the general risk of dystocia (difficult calving) as well as increasing the risk of uterine torsion and decreasing the fertility of the dam if there are any complications. For the sake of the fertility and health of the dam it would make sense to breed calves slightly smaller.
57% of the uterine torsion cases also suffered from retained foetal membranes. Again, it is unlikely that the uterine torsion would cause retained membranes directly; however, this stat is useful to know in order to be able to predict which cows are going to be most susceptible to retained membranes after calving.
55 cases of uterine torsion compared to other types of dystocia, New Zealand:
The first result this study brings to light is that generally cows are more susceptible to uterine torsion than heifers. This is thought to be because of the increased tone of the broad ligaments of heifers and the increased stretching of the myometrium (uterine muscles) of cows – essentially making cows more ‘slack’ inside their uterus compared to heifers. Furthermore, heifers are generally smaller than cows, especially in terms of abdominal cavity size. This is important because of the second result found by this study; foeto-pelvic disproportion decreases the chance of uterine torsion. What this means is that, in comparison to the pelvis of the cow, if the calf is larger than average then the uterine torsion chances are decreased. This is thought to be because the increased size (and not necessarily weight) of the calf, stretches the uterus and fills more of the cavity around it, essentially meaning that there is no room for the uterus to turn or move.
The same point is true for twin births. Because twins take up more space inside the abdomen of the cow, there is less space for the uterus to move around - this is reflected in the results of the study, with only 1 case of uterine torsion reported from a twin birth; however, in general twin births are less common anyway so a correlation cannot be reliably drawn from this data.
This study, along with many others, found that season had no significant effect on torsion numbers. Generally speaking the numbers of cases stay constant all year round. However, it is still possible that in different seasons, different factors affect torsions. For example, during winter, when cows are housed indoors for the most part, the decreased exercise may decrease the tone of the broad ligaments, which will increase the risk of torsion. When spring comes, and cows then go through an increased period of exercise following the period of immobility, the exercise may increase the risk torsion due to the increased movement inside the abdominal cavity. This comes down to the effect of management systems, which is a different story entirely.
It would appear, due to the variation in results comparing the same factor, that management systems play a huge part in the incidence of uterine torsion. In one study, pastured animals were at most risk of uterine torsion, whereas in a different study animals housed indoors were at 3 times more risk of twisted uterus.
When comparing these results it is therefore essential to analyse the management systems too. It is probable that in each system, housed and pasture, there are specific risk factors that predispose to uterine torsion. For example, animals that are housed indoors, as mentioned before, receive decreased exercise – therefore decreasing the tone of the broad ligaments of the cow. Furthermore, if the quality of under-foot terrain is uneven or slippery, indoor housing can increase the risk of slipping and falling, which can be causal of torsions. Cows at pasture may be at increased risk if the pasture is particularly uneven or sloping.
In light of this, the first study which reported increased chance of torsion at pasture may be on a farm in which the pasture is uneven and the second study may have been on a farm with poor shed management.
The study also showed that 90% of the 55 cases were cows that had been kept indoors while on their dry period.
In summary of the above points, the following factors should be kept in mind…
The management of the cow during the dry period should ensure that the cow is receiving enough exercise to keep the ligaments of the cow in tone – if the cow is being kept immobile for a significant amount of time, increase the exercise steadily.
Shed management and layout should ensure that heavily pregnant cows are not going round tight corners, walking over unstable terrain or being squeezed through small gaps – all of which can be events of torsion.
It has been shown that cows calving on their own show decrease numbers of torsion compared to cows calving in small groups. This is most probably due to other cows butting or showing aggressive behaviour towards others. When the cows are in the early stages of parturition, if they are knocked around by others cows, this can cause instable movement and slipping over, causing the uterus to turn.
It would be interesting to assess the effects of housing on one farm. This would eliminate the comparison of management system between farms. Meaning that it would not be the specific layout or terrain of the farms which would be affecting the difference in torsion results. First of all, the number of torsions over 12 months should be recorded in the normal routine of the farm (e.g. cows going out onto a field while dry, then being bought indoors into a small group shed just before calving). After this 12 month period, instead of bringing cows indoors when they are close to calving, allow them to stay outside on a small field close to where they can be monitored. Record the torsion cases of these cows for a 6 month period and then change the system again. Bringing the cows indoors near to when they calve but not allowing group sheds – this would eliminate the issue of aggressive cow behaviour.
This study also found that 80% of calves were in anterior position (coming forwards). This could be because the movement of the calf inside the womb as parturition is initiated could be an essential factor in twisting the uterus.
Report of uterine torsion in cows and buffalo:
This report suggests that many predisposing factors exist for uterine torsion and instead of one factor causing this disease, many play a part in building up the predisposition which eventually takes action during the ‘window of opportunity’. This window of opportunity is during the early stages of parturition when the cow is frequently lying down and standing up.
The factors of predisposition are… management system, lack of movement, insufficient exercise prior to calving and excessive foetal movements. All this elements increase the instability of the uterus.
The direct causes highlighted are lack of mobility followed by high mobility, aggression from other cows e.g. bumping and also cows slipping or falling over.
Eliminating these elements can significantly reduce the cases of uterine torsion seen in a herd.
Speculation from researchers of the studies:
It has been suggested that the increased size of cows in herds nowadays could be a possible reason for the increase in uterine torsion cases. The deeper cavity of cows allows more space around the uterus and gives more chance for the uterus to twist.
Another prospective factor is reduced rumen size just prior to calving; as the uterus rests on the rumen, if the rumen decreases in size, this also allows more space for the uterus to move and become instable. The reason for the rumen size decrease is unknown however it could be due to stockmen intentionally reducing feed intake of cows in late stages of pregnancy.
Conclusions from these results:
· Heavier calves increase the risk of torsion due to increased uterine instability.
· Larger calves in smaller dams decrease the risk of torsion.
· Cows kept indoors for long periods are at increased risk due to lack of ligament tone.
· Cows calving in small groups are at increased risk due to aggression and bumping.
· When cows are frequently sitting up and down this is the most vulnerable point for torsion.
· Specific management systems can be important factors in increasing torsion rates i.e. shed terrain quality.
· Cows are at a higher risk compared to heifers.
How to correct uterine torsions in cattle:
Uterine torsion is seen as an obstetrical emergency and hence is attended on priority. The basic principle of treatment is returning the uterus back to its normal position (this is known as detorsion) which will hopefully lead to vaginal delivery. A foetus in a twisted uterus cannot live for long because of compression of blood supply and it cannot be delivered vaginally until the detorsion has been made.
Before attempting detorsion the general condition of the dam should be improved if necessary. Appropriate fluid replacement, antibiotic and corticosteroids should be given to such animals.
There are 3 treatment approaches to uterine torsion cases, listed in chronological order of attempt…
· Rotation of the foetus per vaginum
· Rolling (and rolling with a plank i.e. Schaeffer’s method)
Rotation of the foetus per vaginum:
This method is best used in mild degrees of torsion where the assistant can touch the foetus and sufficient fluids are present in the uterus. The foetus is grasped by a bony prominence such as the elbow, sternum or thigh and swung from side to side before being pushed right over the opposite direction to the torsion. What this should do is untwist the uterus.
If both limbs are palpable they can be ted in cuffs and an assistant can rotate them. If the manipulation is successful the uterus will untwist and the vaginal tension will unfold.
If there is enough lubrication in the birth canal, the calf can then be delivered by normal vaginal delivery.
It can be helpful to have the cow lying down, as the assistant that is holding the calf swings the calf from side to side, a second assistant should be assisting the rhythm by applying pressure to the outside of the dam’s body, at the position where the uterus is.
In cases of large degrees of torsion or when the problem has not been recognised for a significant period of time, this method will be unusable.
Rolling the cow:
This method utilizes the principle of rolling the cow around its uterus while the uterus remains static. The animal is laid down in lateral recumbency on the same side to which the torsion is directed (i.e. an anticlockwise torsion, a twist to the left, requires the animal to lie on its left side). The two hind legs are tied together by a rope and the fore legs are tied together using a separate rope.
The animal is rolled suddenly (in the same direction as the uterus twist) across onto its other side. The rapidly rotating body of the cow overtakes the slowly rotating gravid uterus. This should untwist the uterus after a few attempts.
Once one roll has been performed, the animal should be slowly and carefully returned to its original position and the process repeated. A maximum number of 4 rolls are recommended.
Often after rolling the cow, the cervix takes another 10-12 hours to dilate.
An addition to this method is Schaeffer’s method; this involves using a flexible, thick wooden plank to secure the uterus as the cow is being rolled. The cow is lay down in recumbency as normal and a plank of wood (ideally 9-2 foot long, 8-12 inches wide) is placed on top of the cow, so that the wood is lying over the top of the uterus. The lower end of the plank should be resting on the ground. An assistant then stands on the lower end as the cow is being rolled. This anchors the uterus in place while the cow is rolled, increasing the chances of the rolling being successful.
This method, also known as a caesarean section, is advisable in cases where manual detorsion has been unsuccessful, the cow’s general well-being is deteriorating rapidly, or the problem has persisted for more than 36 hours.
During the caesarean section the foetus is removed through an incision in the abdominal cavity of the cow.
It is important that the veterinary practitioner receives proper and experienced assistant with this procedure. If the calf is removed from the uterus successfully, the uterus will often untwist back to its normal position, meaning that the incision made in the uterus wall becomes unreachable to the vet – the assistant will often have to take hold of the uterus and hold it in place at all times.
It is essential that the previous two methods are at least attempted prior to a C-section. The above methods have fairly high success rates in most situations, C-section is a last resort.