When emotions run high, hospitals can be dangerous territory for young doctors. Gabriel Weston remembers the day she was forced to choose ethics over impulse

To be a good doctor, you have to master a paradoxical art. You need to get close to a patient so that they will tell you things and you will understand what they mean. But you also have to keep distant enough not to get too affected. This distance keeps both parties safe. A doctor can't afford to faint at the sight of blood or retch on smelling faeces. And the last thing a person wants when they have been told awful news is for their doctor to start crying. But sometimes, your own body declares its fallibility as if in sympathy for the person you are consulting, or your heart defies you by responding just when you least want it to. One of the most difficult things is learning how to manage sexual matters in hospital life. It's like going through adolescence all over again.

The first time I ever touched a stranger's penis, I was lucky enough that the patient was under general anaesthetic. The old man was due for a left hemicolectomy for cancer, a long operation which requires a urinary catheter for monitoring. I was a house officer. I knew I loved being in theatre, but as yet had no useful place in it. I was standing awkwardly in one of the corners when my handsome registrar invited me to initiate myself.

I put on a pair of sterile gloves. "Now," Adonis instructed, "one hand is clean. One hand is dirty. With your dirty hand, swab the penis." Struggling to prevent the words "dirty" and "penis" from conjuring certain private fantasies about myself with this surgeon, I began to blush. I washed the man's glans.

"Now, with that hand, hold the penis still. And with your clean hand take the lignocaine jelly and introduce it into the meatus." I fumbled with the man's limp organ and the vial of jelly, which I hoped would disappear into his penis, poured out all over his groin. Adonis, from his lofty position of experience and romantic obliviousness, began to find my incompetence amusing. "Pull back the foreskin and introduce the catheter." No penis, all foreskin, the task seemed impossible. The slippery prepuce appeared to have no underlying structure to be retracted on so that the end of the foot-long catheter kept popping out of the baggy eye of the man's penis, flicking jelly around with every jaunty boing. Nurses and theatre underlings tittered. Adonis woundingly quipped, "I thought you might have been better at this. Not your first penis, surely?" "My first floppy one, yes!" was all I could hotly reply.

However, if this kind of experience makes one self conscious, far more disturbing is the situation where one's own romantic feelings about a patient get in the way.

As I was shaking out a new white coat from its pack to do my first on-call as a qualified doctor, on the other side of London, a perfect young bricklayer was accelerating his 750cc motorbike to 60 mph on a seemingly empty city road. As the first hours of my on-call disappeared in little tasks and chats, he saw too late the van that pulled out from a side street and knocked him off his bike. Mark hit the ground, bounced several times on to all sorts of different bones, which broke, and then skated noisily across the gravelly surface of the road. He covered a hundred metres of this surface in 10 seconds. Soon afterwards, he reached A&E, where a trauma team was waiting.

Mark had 36 fractures. Some were large single breaks, with others, a single bone had shattered in several places. Amazingly, his skull and face had not been squashed and his internal organs had received no major injuries. His crash helmet and bones had served their purpose.

Two consultant orthopaedic surgeons, each with a registrar, took him to theatre and began to put things back in place, to straighten crooked limbs to stem the bleeding in and outside the bones that was threatening the young man's life.

I was summoned as the underling whose job it was to remove as much as I could of the gravel that had got stuck to Mark's grazed body and face. For this, I was given a large plastic bowl of soapy water and several scrubbing brushes, the ones we use to clean our hands before operating. They have hard, densely packed plastic bristles and I felt quite sick as I was encouraged to rub ever harder, until several brushes had to be replaced by new ones, until the already so damaged man bled in response to my personal assault. The registrar reassured me that I was doing my patient a favour, reducing his risk of infection and of the skin scarring that gravel causes, known as tattooing. After a few hours, I left. I had worn four scrubbing brushes flat.

The next time I saw Mark was on the intensive care unit the following day. His extremities were covered in plaster. Only stripes of skin were visible against the white and these looked swollen, their surface scuffed by my efforts. His head was round with oedema. Round like a child's picture of a head. Not round like a head really is.

His black, heavy-lidded eyes were open a little, like a turtle's, and I saw the globes within them turn in my direction. The half-dead man looked at me and he winked. My heart contracted slightly and my palms prickled. I looked at my colleagues but they were all involved in constructive decision-making. When I glanced back, Mark had looked away.

For the next six weeks, I saw Mark every day and during many nights. I talked to him more than to anyone else. This was my first house job, back at a time when the hospital gave you a bedroom for 12 months on the assumption that you'd be working too many hours a week for it to be worth going home. I saw very little of my friends outside medicine during this time. So, we became friends. He was the one who often encouraged me, at three in the morning, to stop working for 10 minutes to have a cup of tea. He who asked me how trying to become the doctor I was, was feeling. Who told me I was good.

And I filled a gap for him, too, the line between my clinical and personal questions blurring daily. I only realised how odd things had become when a nurse asked me one day if I could check Mark's catheter since he had been experiencing discomfort in his penis and I confessed, to my shame, that I couldn't do the job. I just knew him too well.

As a healthy woman in my twenties, I could not help but notice that, as Mark got better, he was transforming from the swollen-headed broken thing I had first observed into a guy who was the spit of the young Marlon Brando. I began to dread and long for the time when our ortho round would stop at his bedside. I spent one horrible afternoon hovering on the ward trying to work out who exactly his young female visitor was, and what relationship he had with her.

Things reached a climax one night when I was on call. I had spent much of the night in A&E helping out with two trauma patients. The last of these had come in fresh from a road traffic accident and had died soon after arriving in hospital, despite our efforts. It was about five in the morning and my bleep had mercifully stopped bleeping. Usually, I would have gone up to my room. On this day, though, I was feeling jangled by the night so I decided to go to the ward to see if Mark was awake.

I found him sitting up in bed leafing through a motorcycle magazine with his spare, uncasted arm. "You look shagged out," he said, addressing my by my nickname, which he had now been using for a couple of weeks when we were alone.

I sat down and told him the bare bones of what I'd spent my last hour doing. Pumping a man's chest. Feeling his ribs break beneath my hands. Knowing that this didn't really matter because he was dead.

Handsome, Mark faced me with such affection. I looked at his eyes and the thing that usually buffers people's glances when they look at one another fell away and a warmth spread through my chest and made me feel my heart inside me. He lifted his hand from where it lay on the magazine and lifted up the bedclothes and held them about six inches above the mattress. He held my glance, and his eyes and gesture invited me into his bed.

The gesture was so in tune with everything that had gone before, so welcome after the night I had had, that I actually felt my quadriceps muscles tense with the intention my legs had of lifting me from my chair and into the narrow bed alongside him. Then, when instinct halted me and I relaxed back in my seat, a disappointment lay between us. I reached for the hand of his that had made that wonderful opportunity and I squeezed it like I knew a doctor could, hoping that the squeeze would convey all my most undoctorly feelings. Then I got up and went to my room. There I cried. Then I slept for a bit before getting up for the next ward round that morning.

We were both different after that. Mark was getting better and I stopped by to see him less often than before.

On the morning that he left the hospital, I was helping in clinic and when I went up at lunchtime to write up blood results, he was gone. I felt the anger of a jilted one before castigating myself. The next day, a crackly bag with a mother of pearl-coloured surface arrived on the ward with my name on it. Inside was a nest of pink shredded tissue paper and within this some luxury bath products. What you might give to an old lady, but sweeter. As if he were saying, this is an acceptable present but, between you and me, I am thinking of you in the bath.

This is a hospital season. Things don't stay like this for long. You get used to handling patients' genitals so that the only mental shift you have to make is at home, to remind yourself in your personal life that your own private dealings are not meant to be so clinical. With fewer hours at work, you don't have the same intense relationships with patients. But, this initiation into hospital adulthood is useful to have. It brings you down, and makes a fool of you if you try to stand above those you are treating.

This is an edited extract from 'Direct Red' by Gabriel Weston, published by Jonathan Cape, price £16.99