This could refer to many things.
The likely cause is contaimination of the sample, for example by soap, dirt, dust etc.
Biological debris in the urine could mean that there are simply dead skin cells from the bladder or, less commonly casts and dead cells from higher up, such as the kidneys. In men, rarely, it could be retrograde ejaculation where sperm enter the bladder. Another possibility is a passed kidney stone - although these are well known for the extreme pain they can cause, tiny ones that are small enough to move through the uretal tubes often pass un-noticed.
I'd have thought that any biological cause wouold not have stopped the analysis, since the causes above are things that analysis can check for.
When a sample has to be sent for laboratory analysis, this usually means that they want to identify the precise type of bacteria causing the infection so that the most effective treatment can be used. Sometimes infections do not yield or are not completely cleared by broad-spectrum antibiotics or antibacterial drugs. This may be why the infections are repeating; espescially if the first treatment have killed off most of th ebacteria but left the resistant ones behind, meaning the following treatments do not work so well.
I would contact your GP for further advice.
In any case, UTI's are much rarer in men than women because the opening to the outside and the bladder are separated by a much longer distance. This means infective bacteria have far less access. Although elderly men, espescially those with underlying health problems or poor hygiene, are more vulnerable, repeated infections in a man usually result in further investigations because it is regarded as suspiscious, ie, may indicate a problem. Whereas in women such infections are routine and most women get them (even though they may never be aware of it, there are often no symptoms because the immune system deals with the problem)
The most common cause is a prostate problem, unqiue to men (women don't have one). As men age the prostate very often enlarges and this can mean they have problems passing urine effectively. This can lead to infections. The enlargement is usually benign and poses no risk to health aside from problem symptoms. Rarely, there is prostate cancer - this is usually slow growing and unlikely to spread, and in elderly men "watchful waiting" is often adopted, since they are likely to pass away from old age rather than the cancer. But it is watchful because occasionally, the cancer can grow quickly and spread.
Urine is normally sterile and clear, it should be a pale straw colour. Dark urine can indicate the person is under-hydrated. Cloudy or smelly urine usually indicates an infection which needs treating. Blood in the urine is never normal and should always be reported to a doctor urgently.
UTI's can exist and produce no symptoms at all. These are called "sub clinical". However, if the person has dementia, they can still produce the classic signs of increased confusion etc.
