Preventing Urinary Catheter Blockages

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Preventing Urinary Catheter Blockages

Post by Barry » 4 years ago

Part 1 of 2


I had 23 catheter blockages between January and July 2016.  Then I found a way of stopping them.  I have had none since.  This has left me with the impression that blockages have been too readily accepted as a normal part of having a catheter.  They are an additional misery for people who, in many cases, have other serious conditions; they are more dangerous than is widely recognised and waste a great deal of nursing time unblocking catheters which do not need to be blocked.
Here is the method which stopped my urinary infections and catheter blockages immediately, completely and without any noticeable side-effects.  I do not know for how many others it would be suitable.

It's coming up to 1'o clock in the morning. I waken up sweating profusely.  I'm getting tremendous shocks of spasms.  I have an overwhelming urge to move my legs but I can't.  I can't move:  following a spinal injury in 2013, I have been paralysed from the shoulders down.  I fumble round the bed to find the 'phone. Eventually I find it, despite very little movement or sensation in my hands, now clawed up like an animal's paws.  With my knuckles and a protruding little finger, I 'phone for a nurse, desperately trying to hold the 'phone to my ear.  Fortunately a kind and thoughtful nurse had previously given me their direct number so that I don't have to endure the 111 service.  The spasms and sweating are becoming even more severe.  By the time she arrives, which can be over two hours later, the bedsheets are wet with sweat.  'Sorry I took so long.  I've had a lot of catheter blockages tonight'.
Another one: between the nights of 16/17th January and 23/24th July 2016 I had 23 like that, typically between about midnight and 1am - long enough for urine to build up if my catheter had actually become blocked immediately after going to bed. 

I had a suprapubic catheter installed in May 2013.  I had no blockage for the first two years and eight months.
At least two-thirds, but not all of my blockages were accompanied by sediment in my catheter.  The last two blockages both occurred on the night of 23/24th July 2016.  My catheter was replaced after the first of these.  The second blockage was described by the nurse as 'positional'.  Attending an earlier blockage, a different nurse had suggested that a possible cause was the catheter intake pressing against my bladder wall.  So there seemed to be at least two causes of the blockages: by sediment and by the position of the catheter.
Why were all my blockages shortly after changing positions from sitting in my wheelchair to lying flat in bed?  That is a better question than is my answer to it.  The positional blockages were likely to have been caused by my catheter coming up against my bladder wall or the intake becoming too low for drainage of urine by gravity.  The sedimentary blockages might have resulted from the catheter moving to a lower part of my bladder where sediment had collected.
Late on the morning of 24th July I began sweating heavily and my spasms became more severe.  I took these to be signs of a urinary infection: I took 50mg Nitrofurantoin and it was soon cleared.  This was not the first time that symptoms of an infection followed a blockage.  It appeared that the bacteria causing the infections were also creating the sediment which caused most of the blockages.  So using Nitrofurantoin to prevent infections (rather than to cure them) in my case, also prevented catheter blockages.  From the evening of 24th July I started taking 50mg Nitrofurantoin each day at about 8pm.  I have had no blockage since. 
In these circumstances, I try to maintain an awareness of the symptoms of septicaemia, the infection, and sepsis, the body's inflammatory reaction to it and to be aware that urinary infections can develop into septicaemia and sepsis: ... ction.aspx
and because I have a spinal injury, also autonomic dysreflexia: ... c-overview


May 2013 to 15th January 2016: no blockage; Nitrofurantoin taken occasionally to cure urinary infections.
16/17th January 2016 to 23/24th July 2016: 23 blockages; Nitrofurantoin taken occasionally to cure urinary infections.
Since March 2016: weekly bladder wash-outs.

Since 24th July 2016: no blockage;

50mg Nitrofurantoin taken on these evenings to prevent infections and blockages:

July 24-31;
August 1-22, 24, 25, 26, 28, 29, 30;
September 1, 2, 4, 7, 8, 10, 13, 16, 18, 19, 22, 25;
October 1, 5, 6, 7, 11, 14, 15, 17, 20(100mg), 21, 22, 23, 25, 29, 31;
November 4, 5, 7, 10, 13, 16, 19, 22, 24, 26, 28;
December 1, 3, 5, 8, 11, 12, 17, 22, 31;
January 8, 16, 18, 22;
February 5, 13, 16, 20, 25;
March 11, 25;
April 2, 8, 13, 22, 28;
May 1, 12, 19;
June 3, 13, 18;
July 2, 10, 23,

Catheter repositioning to prevent non-sedimentary blockages.

Since January 2017: rolling catheter between hands and consumption of natural antibiotics: lemon tea, vinegar on food.


What about the blockages not caused by sediment - the 'positional' blockages?  To prevent these I simply gently pull my catheter forward each night immediately after going to bed to pull it away from my bladder wall.  At the same time I also unstrap the catheter and leg bag from my leg and lay it flat on the bed to help gravity by ensuring that as much of my catheter as possible is at a lower level than the intake.
The Users' Information Leaflet says that the normal dose of Nitrofurantoin for preventing infections is 50mg or 100mg daily at night but does not say for how long.  On the principle that it is best not to take more medication than necessary, after 30 days taking 50mg, I began tentatively to omit it on a few nights and risk the horror of a blockage.  For about 3 months I took 50mg on 3-4 nights per week and then reduced it further to only nights when I had a considerable amount of sediment in my catheter or sweating which could warn of a urinary infection.

The district nurses started giving me weekly bladder wash-outs soon after my blockages started: so the first few nights I omitted Nitrofurantoin were wash-out days.  Wash-outs probably reduced the number of blockages but did not eliminate them.  Not long after I reduced Nitrofurantoin to less than every night, I did begin to get sediment in my catheter.  This seems to have been kept in amounts insufficient to cause a blockage by carers rolling the catheter between their hands to disturb it and by consuming natural antibiotics, including adding vinegar to food and drinking lemon tea (not surprising - the bladder wash-out solution contains citric acid).  To make lemon tea, I simply cut an unpeeled lemon in half, cut up the half into pieces or slices put in a cup and add hot water, topping up several times and squeezing the lemon with a spoon.  Lemons can be used in many other ways too: ... emon-peel/
I will never know whether rolling my catheter and taking natural antibiotics would have been sufficient to stop the blockages without Nitrofurantoin.  I started them in January 2017, six months after my blockages had been stopped.  However, it does appear that they have allowed a reduction in the dose.

Could something else have stopped my blockages immediately, completely and for such a long time?  All I can say is that I am not aware of doing anything else on and following 24th July that could be expected to stop blockages other than taking Nitrofurantoin and catheter repositioning.

Although I have had no blockage since the night of 23/24th July 2016, often I have sediment in my catheter.  When this looks sufficiently severe to risk a blockage, I take 50mg Nitrofurantoin about 8pm.  Within an hour or two, the sediment is reduced or has gone completely.
I had 23 blockages in a period of 190 days from 16th January to 24th July 2016, no blockage since (365 days up to 24th July 2017).  The probability of Nitrofurantoin and catheter repositioning having had no effect can be calculated as the probability of 23 random occurrences in a period of 190+365 days all being in the first 190 days. 
The probability of any one of them being in the first 190 days is 190/(190+365) = 0.3423;
considering any two of the blockages, the probability of both of them being in the first 190 days would be 0.3423 x 0.3423 and so on until  .....
the probability of all 23 being in the first 190 days is 0.3423 multiplied by itself 22 times = 1.95595e-11 = 0.0000000000195595 which is a little less than 2 chances in a hundred thousand million (a hundred thousand million is the number that 0.0000000000195595 would have to be multiplied by to get 1.95595). ... ulator.htm
The base is 0.3423 and the exponent is 23.
So the probability that Nitrofurantoin and catheter positioning were not associated with stopping blockages is 0.0000000000195595; therefore the probability that they have been associated with stopping blockages is 1 - 0.0000000000195595 = 0.9999999999804405 where absolute certainty equals 1.
The binomial distribution can also be used with the same result:

where N = 23, k = 23, p = 0.3423 and the answer is p(k out of N)

The multinomial distribution can be used too: ... bution.php
where the number of outcomes is 2 (blockage on a day in first 190 days /blockage a day in following 365 days), the number of occurrences 23 and 0, p = 0.3423 and 1-0.3423 = 0.6577.
These calculations are based on cautious assumptions.  The probability of there being no association between taking Nitrofurantoin and the absence of blockages is likely to be even smaller than the very small probability of 1.95595e-11.  On about 10 of the 190-day period with blockages I took Nitrofurantoin to cure urinary infections.  I had no blockage on these days.  So there is a case for reducing the period to 180 days, or fewer if the effect of Nitrofurantoin lasted for more than one day, and adding 10 or more days to the blockage-free period.  If the period were reduced to 180 days, the probability of all 23 blockages being in the first 180 days would become (180/(180+375)) to the power 23 = 5.6465e-12. 

There is no practical difference between using a period of 190 days, 180 days or fewer.  In all cases the probability of all 23 blockages being in this period by chance is so small as to be negligible.  This very small probability means that it is practically certain that Nitrofurantoin and catheter repositioning were associated with stopping my blockages; it is not the probability of having a blockage tonight; nor is it a prediction of when a blockage can be expected.


Prediction methods rely on making inferences from the past: so while the treatment is never followed by a blockage, the prediction will remain zero for any period into the future.

However, where treatment sometimes fails, any of several methods can be used to estimate when future failures will occur.

If I were to have a blockage, the negative binomial distribution, also known as the Pascal distribution, could be used to predict the probability of a further blockage on each of the days following. ... omial.aspx

The number of trials is the number of days after the first blockage, the number of successes is the number of blockages to be predicted (1 if the next blockage is to be predicted, 2 if it is to be the blockage after that and so on), probability of success on a single trial would be 1 divided by the number of days between the start of my blockage-free period and the first blockage and the negative binomial probability is the probability of the chosen blockage (1st, 2nd or whatever was chosen) occurring on the chosen number of days after the first blockage. 

A cumulative version, which can make some calculations less laborious, is available at: ... stribution

The geometric distribution is a particular case of the negative binomial distribution where the number of successes, in my case, blockages, is equal to 1: so if the timing of only the next blockage is to be estimated, it can be used instead of the negative binomial distribution. ... &k=6&p=0.5

Here, the number of successes is the number of days without a blockage before the next one occurs, the probability of success is as for the negative binomial distribution and the maximum number of trials is the number of days for which you require the probability to be calculated.  This calculator can save time by using the probability mass function, which shows the probabilities of a blockage on the days leading up to the day chosen.

It is possible to predict the number of blockages within any specified period using the Poisson probability distribution: ... aspx. 

For example, suppose we wish to predict the chance of 1 blockage in a period of 7 days, the Poisson random variable would be 1.  The average rate of success is the average number of blockages which in the past have occurred in 7 days (number of blockages/number of days in observation period x 7). To predict the chance of 2 blockages in 28 days, the Poisson random variable would be 2 and the average rate of success would be the average number of blockages in 28 days.  As long as there are no blockages on nights following taking Nitrofurantoin, the average number of blockages for any period is 0: so until there is a blockage, the prediction of future blockages for any period is zero.

The negative binomial distribution, the geometric distribution and the Poisson probability distribution rely on the events (blockages in this case) being independent - not connected to each other, even indirectly by a common cause - and randomly distributed.  This is liable to introduce inaccuracies into the predictions if the connections are not taken into account.  On the other hand, if predictions from these techniques do not fit observations, that will be evidence that there are connections between the events (blockages) and that there is likely to be a common cause.

It might seem inconsistent that the effectiveness of Nitrofurantoin and catheter repositioning was demonstrated by the lack of randomness in the distribution of the 23 blockages between the 190 days without the treatment and the 365 days with it, while the techniques for predicting future blockages rely on them being randomly distributed.  Not necessarily so; the predictive techniques would be used only in the period when the treatment is taking place.

......  continued as part 2
Last edited by Barry on Sun Aug 06, 2017 10:43 am, edited 1 time in total.

Posts: 15
Joined: 4 years ago

Post by Barry » 4 years ago

Part 2 of 2


I do not have a good answer to this.  I had my catheter for 2 years and 8 months before I had a blockage.  This period included about a dozen urinary infections.
On the evening of 16th January 2016 I was overheating so I took 500mg Paracetamol.  That was the first time I had taken any since my catheter was installed.  A few hours later I had my first blockage.  The coincidence looked too close to believe that the Paracetamol had not played a part.  I took no more Paracetamol but continued to have blockages about a week or ten days apart.  After a few of these I convinced myself that they had nothing to do with Paracetamol: on 16th January I had a urinary infection and should have taken Nitrofurantoin instead of Paracetamol.  So I left this out of the earlier paper: ... s.doc         ... kages         
Nevertheless, I have taken no more Paracetamol.

Even without an analysis of the contents of my catheter at the time of a blockage, it is possible, by using a filtering process and information from the Internet, to identify the most likely bacterial culprits for my blockages.  This might be important in identifying what other antibiotics are likely to be effective in preventing blockages for those who have an adverse reaction to Nitrofurantoin.

The filtering process comprises three stages:

1  Against what bacteria is Nitrofurantoin effective?
Before the blockages started I had more than a dozen urinary infections, readily stopped by Nitrofurantoin. 
Nitrofurantoin has been shown to be effective against the following bacteria:
Citrobacter species, Coagulase negative staphylococci, E. coli, Enterococcus faecalis, Klebsiella species, Staphylococcus aureus, Staphylococcus saprophyticus, Streptococcus agalactiae
Many or all strains of the following genera are resistant to Nitrofurantoin: Enterobacter, Klebsiella, Proteus, Pseudomonas

Obviously, whatever bacteria caused the pre-blockage infections did not create enough sediment to cause a blockage.  These bacteria must be on the Nitrofurantoin hit list; so too must those that did cause blockages, but they were not necessarily the same ones or in the same concentrations as those that did not cause a blockage.

2  It has been established that most of my blockages were associated with urinary infections, so which of these bacteria cause urinary infections?

E. Coli and Proteus mirabilis are often the cause of urinary infections: ... rs&spf=395 ... tions-utis

'Escherichia coli or E. coli, is responsible for more than 85 percent of all UTIs, according to a 2012 report in the journal Emerging Infectious Diseases.
Several other common bacteria also cause UTIs, including Staphylococcus saprophyticus, Pseudomonas aeruginosa and Klebsiella pneumonia.' ... infection/

Pseudomonas, Klebsiella and Proteus are on the list for which Nitrofurantoin is not likely to be effective: so that leaves us with E. Coli and Staphylococcus saprophyticus.

3  Which of these bacteria cause sediment which could block a catheter?
Cloudy urine, but not sediment, is mentioned as a consequence of E. coli. ... infection/

Sediment is associated with Staphylococcus saprophyticus:

That leaves Staphylococcus saprophyticus and E. coli as the prime suspects.  Although Staphylococcus saprophyticus is the better fit to the information I have been able to find, E. coli is a much more common cause of urinary infections. Without any analyses of the contents of my catheter at the times of infections with or without blockages, it is not possible to be sure. 

Because Nitrofurantoin is effective against some of the bacteria which cause urinary infections and which also create sediment in urine, it should not come as a surprise that it prevents some blockages associated with urinary infections.

I can only guess how many of my blockages could have been avoided if taking a sample of the contents of catheters were standard practice when a blockage occurs.
There might have been other mechanisms starting the blockages: an increase in urine pH, a change in brand of catheter  .....

What I have reported is, of course, my own story.  I do not know for how many other people it might be effective but there seems to be a reasonable expectation that it might work for others - male or female - whose catheters are being blocked by sediment created by bacteria for which Nitrofurantoin is effective.

So it seems that blockages caused by bladder stones would not be prevented by Nitrofurantoin because the bacterium involved is Proteus mirabilis: ... 1032a.html

Nitrofurantoin will not be suitable for everyone.  The Users' Information Leaflet lists many precautions and possible side effects.  I have not had any at the doses explained but others might.  Nitrofurantoin was used to stop the bacterial blockages simply because it was the only antibiotic I had.  Some web sites suggesting other antibiotics for Staphylococcus saprophyticus, E. coli and other bacteria causing urinary tract infections are as follows: ... ction.aspx ... ns&spf=396

Catheter blockages are at least distressing, especially if experienced help is not quickly available.  Uncertainty about when help will arrive adds to the distress.  I had to wait between about 40 minutes and 2 hours 15 minutes with the sweating and spasms progressively becoming more severe.
Is there likely to be any lasting or permanent damage?  I am not aware of having any myself but serious kidney and bloodstream infections, septicaemia and autonomic dysreflexia have been experienced by others: ... /blockages
How many deaths result from catheter blockages?  We are not likely to get an accurate estimate because some of them are liable to be recorded as autonomic dysreflexia, sepsis or something else.  Recorded deaths from sepsis are many and increasing: ... epsis.aspx ... eet_DE.pdf
It has been estimated that about 2,100 deaths per year result from the Foley catheter (but not all resulting from blockages?): ... infections
About 450,000 people in the UK have permanent catheters and as many as a half of these experience 'recurrent infections with blockages and leakages': ... theter.pdf
The same paper quotes that 'In the UK, permanent catheters are used by 3% of people living in the community and 13% of care home residents'.


The nurses, particularly the night nurses, have left me with the impression that catheter blockages are much more common than they need to be.  Often, they left me with a cheery 'See you again soon'.  The prevailing attitude in both the medical and nursing professions that they are an inevitable consequence of having a catheter should be questioned. 

In November 2016 I 'phoned the night nurses to thank them for coming to unblock my catheter on 23 nights between January and July, to explain why I have not called them out since July, and to offer to send them a copy of this paper: 'We don't give out e-mail addresses over the phone'.  This was particularly disappointing because their own records of nursing call-outs will confirm the veracity of the data on which this article is based.

Meanwhile, patients wake in the early hours of the morning, sweating profusely, trembling with massive shocks of spasms, resulting in urine being forced back to the kidneys and in extreme cases, autonomic dysreflexia, internal damage and death. Night nurses rush between patients to unblock catheters which do not need to be blocked. Sometimes they have taken over 2 hours to reach me (although the average is about 1 hour 20 minutes).

Recently, a nurse from the local health authority called to assess my condition. A friend who was with me mentioned my catheter blockages and offered her this paper: no thanks. 'It's something they can live with'.

During the course of preparing this paper I have had correspondence with many people connected to the medical or nursing professions, including organisations representing patients.  Although no-one else has used those exact words, 'something they can live with' sounds chillingly close to the attitude to so many of the responses (or lack of responses).

Such has been the resistance to an approved dose of an approved medication.  How much greater can we expect the difficulties of improvement in the medications available for spasms for example, or equipment such as catheters, when those needing them have been conditioned to expect nothing better than what they are given, when manufacturers are allowed to happily continue to sell the same old products.  I must say I am left wondering whether the brick wall of complacency about catheter blockages also applies to other treatments and equipment that those with spinal injuries need - including treating the injury itself - and beyond spinal injuries. ... aints.html


1  Catheter blockages are not something to accept as inevitable. Some of them are preventable.

2  Greater priority should be given to prevention in order to reduce the need for firefighting.

3  A small amount of resources devoted to preventing catheter blockages seems likely to result in a handsome pay-off in terms of savings in time spent unblocking catheters and unnecessary hospital appointments.

4  They are much more serious than is sometimes recognised among both the medical and nursing professions.

5  Prevention of catheter blockages has not had the priority it merits.  Nurses could advise patients on preventing those caused by physical obstruction. 

6  The method outlined worked for me but might not be so successful for some others.  Nitrofurantoin can not be expected to prevent blockages caused by bladder stones for example, because it would not be effective against Proteus mirabilis, the bacterium involved.

7  Nitrofurantoin might have unacceptable side-effects for others as set out in the Users' Information Leaflet. 

8  Samples of catheter contents should be taken when there is a blockage to identify what bacteria or other causes were responsible.  This should lead to much earlier and more accurate diagnosis of the cause and what action to take.  It can also be expected to reduce the suffering and damage to patients, waste of nursing time unblocking catheters which do not need to have been blocked and unnecessary hospital appointments resulting from wrongly guessing the causes of blockages in the absence of evidence. 

9  The methods which worked for me could be offered to others with catheter blockages if there is no reason to believe that Nitrofurantoin would be unsuitable for them, particularly if samples of catheter contents have been analysed and found to contain bacteria against which Nitrofurantoin is effective, such as Staphylococcus saprophyticus or E. coli.

10  Depending on the results of analysis of samples from catheters at the time of blockage, it might be worthwhile to investigate the possibilities of using other antibiotics for those for whom Nitrofurantoin has undesirable side-effects or whose catheters have been blocked by sediment created by bacteria not on the Nitrofurantoin hit-list.

11  Blocked catheters are at least traumatic, at worst they are killers, they are expensive in terms of nursing and other medical staff time and resources and occur on a scale which makes them one of the most common healthcare problems.  Some of the papers quoted in the previous section make the often-heard call for better catheters, which would empty the bladder completely and so reduce infections and blockages.  Sadly, it is no surprise to read this, but until they are available, there remains a need for preventing blockages in the catheters which we have.

12  So far I have not found any decrease in the effectiveness of Nitrofurantoin with continued use or with irregular dosage.

P.S. Still no blockage since the night of 23rd/24th July 2016.                                                   
                                                  24th July 2017
Last edited by Barry on Wed Jul 26, 2017 10:13 am, edited 1 time in total.

Posts: 15
Joined: 4 years ago

Post by Barry » 3 years ago


I have still not had a catheter blockage since the night of 23rd/24th July 2016.

Neither have I had a serious urinary tract infection.

My catheter blockages were being caused by urinary tract infections of Staphylococcus saprophyticus and/or E. coli; these caused the sediment which led to the blockages. Using Nitrofurantoin as a prophylactic has controlled the bacteria and so the production of sediment to levels below that needed to cause a blockage.

There have been a few occasions when I have had a limited amount of overheating which might have been minor urinary tract infections. These were accompanied by sediment in my catheter. I have treated these by taking just one 50mg tablet of Nitrofurantoin, or for very minor overheating, lemon tea and vinegar on food. It appears that they have allowed a reduction in the dose of Nitrofurantoin, but in the amounts I have been taking (1/2 lemon and 30ml. vinegar per day) they would probably not be sufficient alone. For example, on the evening of 9th February 2018 after consuming the usual amounts of lemon and vinegar, my catheter had a large amount of sediment in it: so I took 50mg. Nitrofurantoin: the following morning it was clear.
There is usually some sediment in my catheter. I loosen this when going to bed by manipulating and bending the catheter, or if there is an amount which looks sufficient to threaten a blockage, I take 50mg Nitrofurantoin.

If others try these methods without success, it is likely to be because their blockage was caused by a different bacterium not on the Nitrofurantoin hit-list. In such a case, it would be advisable to request an analysis of their catheter contents at the time of the blockage and then use a different antibiotic to control it.

It is likely that the method can also be used to control UTIs in those who do not have blockages.


May 2013 to 15th January 2016: no blockage; Nitrofurantoin taken occasionally to cure urinary infections.

16/17th January 2016 to 23/24th July 2016: 23 blockages; Nitrofurantoin taken occasionally to cure urinary infections.
Since March 2016: weekly bladder wash-outs.

Since 24th July 2016: no blockage;

50mg Nitrofurantoin taken on these evenings to prevent infections and blockages:

July 24-31;
August 1-22, 24, 25, 26, 28, 29, 30;
September 1, 2, 4, 7, 8, 10, 13, 16, 18, 19, 22, 25;
October 1, 5, 6, 7, 11, 14, 15, 17, 20(100mg), 21, 22, 23, 25, 29, 31;
November 4, 5, 7, 10, 13, 16, 19, 22, 24, 26, 28;
December 1, 3, 5, 8, 11, 12, 17, 22, 31.
Total for July - December 2016: 84x50mg

January 8, 16, 18, 22;
February 5, 13, 16, 20, 25;
March 11, 25;
April 2, 8, 13, 22, 28;
May 1, 12, 19;
June 3, 13, 18;
July 2, 10, 23;
August 14, 15;
September 17, 18;
October 11, 17;
November 2, 14;
December - none. Total for 2017: 33x50mg

January 5, 22, 31;
February 9, 15;
March 2, 9, 10, 17
April 8, 9, 23, 29
May 12
June 11, 16
July 1, 16

Catheter repositioning to prevent non-sedimentary blockages.

Since January 2017: rolling catheter between hands and consumption of natural antibiotics: lemon tea (half a lemon), 30ml. vinegar on food.

29th July 2018

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