Drain Pain, Overfill, and How They Are Connected

Drain pain and overfill are two complications of peritoneal dialysis (PD) that get very little attention in the published literature. A “PubMed” search reveals no articles about PD with ‘drain pain’ in the title and only one addressing ‘overfill’ in the sense of an excessive intraperitoneal dialysate volume (1). Are these complications both rare? Or are they trivial curiosities not worthy of more clinical attention? This commentary will argue that one of the two is very common, that both need to be understood better, and that they have recently become related in an unforeseen way.

Despite the lack of published reports, this author has been struck by how common drain pain is in contemporary PD. A paper from our group, published in this issue of PDI and based on a survey of 293 automated PD (APD) patients in 6 sizeable PD programs in the Canadian province of Ontario, shows that 72 or 25% of these patients are using a tidal modality of PD, specifically because of drain pain (2). This indicates a widespread problem. The survey is likely representative in that it comprises approximately 15% of the PD population of the province and in that the Baxter cycler being used in all these centers was dominant in the Canadian PD market. It also seems a reasonable assumption that the drain pain had to be of significant severity to become an indication to switch to tidal PD. If anything, the prevalence of the problem may be understated because some APD patients may manage without converting to tidal, others may switch to continuous ambulatory PD (CAPD) because of the pain and still others likely drop out of PD altogether.

There is also a strong impression that drain pain is much more common now than was the case a decade or two ago although there are no studies to prove this. Why might drain pain have become so common and what is causing it? First, it is largely a complication of cycler PD. Contemporary cyclers use hydraulic suction rather than gravity to drain dialysate and drain pain is thought by some to be caused by the consequent application of negative pressure to the very sensitive parietal peritoneum toward the end of each drain cycle. This leads to referred pain, often quite unpleasant and felt in the rectal or genital areas. Others speculate that the pain is related to negative suction on the external bowel wall.

However, hydraulic suction cannot be the only factor as there is a marked ‘center effect’ in the prevalence of drain pain. Thus, the Ontario survey shows marked variation from as few as 4% having the problem at one site to as many as 37% at another (2). This suggests a relationship to how peritoneal catheters are placed. Crabtree has speculated that drain pain is more likely to occur if the intraperitoneal portion of the catheter is too long, due to the insertion site being too low in the abdomen relative to the patient’s pelvic anatomy (Crabtree, Personal Communication). The tip of the intraperitoneal portion of the catheter is then more likely to lie against the parietal peritoneum toward the end of the drain when the suction induces pain. This suggests that more attention to the length of the catheter used and to the insertion site might decrease the problem (3). Are there other factors? Our survey did not collect sufficient detail to look for interactions with age, sex or, perhaps, body mass index. Could some of the apparent increase in frequency of drain pain reflect an increase in the prevalence of obesity among PD patients?

Management of drain pain is a challenge and, in severe cases, patients will often give up PD and shift to hemodialysis. The initial approach in an APD patient is to use laxatives to treat any constipation and see if this helps by allowing the catheter to move into a better position. The next step is to introduce tidal PD, starting with perhaps 85% tidal and increasing to 75% and even 60% until the pain resolves. If this is insufficient, a switch to CAPD is often effective as the gentler gravitational drains of that modality are much less likely to induce discomfort. However, for some patients, CAPD is seen as more intrusive on lifestyle and so, if tidal PD is ineffective, a switch to hemodialysis becomes attractive. Introduction of normal pH ‘biocompatible’ solutions is an effective intervention for the much less common complication of infusion pain but is ineffective with drain pain (4). Some patients develop their own approaches, aborting the hydraulic drain or regulating it by squeezing the drain tubing. While tidal PD is usually effective in resolving or at least lessening drain pain, challenges can arise and these have recently become more complicated. To understand this we need to consider a second complication of PD. This is the issue of ‘overfill.’

Overfill is defined as a clinical event in which symptoms of raised intraperitoneal pressure occur in association with a high drain volume to fill volume ratio (DV/FV) with the implicit notion that the drain volume is the end-dwell volume. Anecdotally, most experienced PD practitioners have seen episodes of overfill but most would probably say that these events were curiosities rather than significant concerns and rarely caused harm. However, in 2012, Davis et al. from Baxter Healthcare published a review of overfill events based on data from a US Food and Drug Administration website that collects data on medical device malfunction (1). Ten deaths were identified that occurred in association with episodes that were suspicious for overfill. Three of these had convincing data on DV/FV with values of 2.28, 2.50 and 3.33 respectively. Association is not cause and effect and, given that over 150,000 patients received PD in the US during the time period concerned, the occurrence of between 3 and 10 deaths at the time of these episodes could represent coincidence. However, in some of the more extreme cases recounted, a suspicion of causation seems justified. For example, in one case, the patient had been doing APD and had repeatedly filled with 2-L dwells without draining adequately until he was found dead with 5 L in his abdomen. However, many events where the DV/FV was high caused very minor symptoms and the variability of the relationship of DV/FV with symptoms was noted. Over 80% of suspected significant overfill events were related to insufficient drains while much smaller numbers were due to excess infusion, device malfunction or excess ultrafiltration (1).

This issue of PDI provides further data from these Baxter investigators. Cizman et al. used data from Baxter Healthcare cycler device log files to look for episodes of overfill (5). There was no information on associated symptoms so the investigators used a definition of DV/FV > 1.6 for Level I or mild overfill and of DV/FV > 2.0 for Level II or more severe overfill. A number of interesting observations are made. In adult APD patients, Levels I and II overfill occurred in 2.39% and 0.26% of treatments respectively—not common but certainly not rare. Rates were more than twice as high in pediatric cases and were 3 to 4 times higher in tidal PD. In standard APD, rates were higher if initial drain volume targets were programmed to be less than 70% of last fill volume, if minimum drain volumes were programmed to be less than 85% of fill volume, if the initial drain was bypassed, or if ultrafiltration was greater than 1.245 L. With tidal PD, not setting total ultrafiltration targets above zero led to twice the rate of overfill events (5).

A few comments need to be made. First, the database may not be representative of APD in general as many of the device log files came from cyclers that were reviewed precisely because there were complaints about them. Also, there is no information on symptoms or consequences of these ‘episodes’ but clinical experience plus the Davis paper findings suggest these are uncommon. Most of the predictors identified were what one might expect. It is not really surprising that overfill is more likely with greater ultrafiltration or with bypass of drains. The association of tidal PD with overfill may not be cause and effect but rather may mainly reflect the common association of both tidal PD and overfill with a poorly functioning catheter, the true cause of the problem. The paper does not tell us how frequently harm results from any of this but it does, however, give an unprecedented and interesting insight into how frequent, or infrequent, marked rises in intraperitoneal volume are in APD. A useful fact for the clinician to retain is that about 1 in 400 APD sessions in this study was associated with an episode in which dwell volumes doubled compared to initial fill volume i.e. typically from 2 to 4 L.

How does all this relate to drain pain? The crux of the issue is that the identification of tidal PD and of bypassing initial drains as a risk factor for ‘overfill’ has led Baxter, and may lead other PD companies, to re-engineer their cycler software to limit the extent to which tidal PD can be successfully used as a means of avoiding full drains and consequent drain pain. Thus the newest model of the wellknown Home Choice (Baxter, Deerfield, IL, USA) cycler now requires the so-called ‘initial drain’ that a patient does after first hooking up to the cycler to be completed without any bypass before cycling can commence. For those with drain pain, this creates a problem in that the mandatory complete drain makes the pain inevitable and sometimes severe. Fortunately, this requirement only applies to the initial drain and all subsequent drains can be done in tidal mode but, in practice, this alteration in the cycler means that in order to prevent a rather rare complication, a very common one may be aggravated. This is unfortunate and the question arises as to whether it is justified. Obviously, fear of adverse events and of liability and regulation has to be taken into account with all medical devices and technologies but pain suffered by kidney patients is not a trivial issue. To paraphrase, the prevention of overfill may be causing more cumulative distress than the condition itself ever did.

There is a further modification to Home Choice cyclers that may be relevant to the patient using tidal PD to prevent drain pain. The cycler has long had a ‘Tidal Full Drain’ option that many centers use routinely with tidal PD. The issue is that if the tidal volume removed is kept constant during cycling at, for example, 70% of an initial 2-L fill volume, then as serial ultrafiltration occurs with each cycle, the residual volume of fluid in the peritoneal cavity will rise as the treatment proceeds. So, if the patient on 70% tidal and a 2-L initial fill has a total cycler ultrafiltration of 1 L, the residual volume will rise from 1.4 to 2.4 L by the end of the cycling session and the peak intraperitoneal volume during the final cycle may be close to 3 L. To avoid this, many centers use the ‘Tidal Full Drain’ option to program a full drain to occur with every third or fourth cycle. However, for the patient doing tidal PD to avoid pain, this may lead to one or more painful episodes during the night. This can be avoided by not activating the option. Ultrafiltration is often less than 1 L per night and, in any case, transient dwell volumes of up to 3 L seem to be tolerated by most such patients and may be preferable to being woken with drain pain. The point for the practitioner to be aware of is that the ‘Tidal Full Drain’ option needed to be activated in the older 10.2 model of the Home Choice but, in the newer 10.4 version, it is on by default and needs to be deactivated if the clinician judges this to be appropriate to prevent drain pain in the middle of the night.

What are we to conclude from all this? It appears that while ‘overfill’ as measured by high DV/FV is not rare, serious morbidity or mortality associated with ‘overfill’ is very infrequent. Drain pain, in contrast, is very common. A database collecting information on device malfunction may only record overfill episodes even though drain pain may be much more frequent. Therefore, one might argue that the requirement for mandatory complete initial drains may cause more problems than it solves. Perhaps a special restricted code to override the initial drain requirement in the minority of patients who suffer uncomfortable drain pain would be a good compromise. Of course, a better solution to this conundrum is for centers with high rates of drain pain to address their problem but how is this to be done? If, as Crabtree proposes, drain pain is mainly due to too much of the peritoneal catheter being ‘bunched’ into the pelvis, then an approach based on correcting this by altering the insertion site needs to be studied to see if it solves the problem.

Drain pain is not a life-threatening problem. To centers that have a low rate of drain pain this may seem like a lot of fuss about nothing very much. But to the significant group of patients who do have the problem, recent changes in the cycler may be adding one more painful burden to the already impaired quality of life that dialysis patients have to cope with. The issues here may not be glamorous, but for those who suffer with them, they are important and should be addressed.

Disclosures

The author has received research support from Baxter.